But many corporate information-technology departments have refused to buy the phone. Why? Because the Treo is powered by the Palm operating system and not by software from Microsoft, the only company whose software is supported by many IT departments.

So Palm this week introduced a Treo model that uses the latest version of Microsoft’s Windows Mobile software (formerly known as Pocket PC). On the outside, the new Treo 700w looks very much like the current Palm-based model, the Treo 650, which will remain on sale and will continue to be developed on a parallel track. On the inside, though, the new Treo’s key software functions — phone, email, Web, multimedia — are all different.

I have been testing the Treo 700w, which will be sold by Verizon Wireless, to see how it stacks up against the Treo 650, the phone I carry every day.

My verdict: Despite some nice new features, the Windows Mobile software is still inferior to the Palm software for one-handed use on the go. Its crucial email and phone functions are also weaker. And there’s a serious bug in its email software that affects individuals, though not corporate users. So the Treo 700w is neither as easy to use nor as powerful as the Treo 650. In addition, the screen on the 700w offers significantly lower resolution than the screen on the 650, and the new model costs twice as much — $400 versus $200.

For individual users, the main advantage of the new Treo 700w is that it is the first Treo to work on Verizon’s high-speed EV-DO network. That network delivers data speeds that rival those of home DSL lines. But the speed advantage will be short-lived, because I expect to see a Palm-based Treo in coming months that can also use the EV-DO network.

At first glance, the phones look nearly identical, though the new 700w is a bit more rounded. The key dimensions are all the same, but the color scheme is a bit different and the 700w has a slightly better keyboard. The individual keys are squarer, with a bit more room between them.

The built-in camera on the new model is much better than the primitive one on the 650. It can shoot at a resolution of 1.3 megapixels, up from just a third of a megapixel for the older camera. In my tests, the 700w’s pictures were much better. But the resolution of the screen on the 700w, a vastly more important component, has changed for the worse. Although it is about the same physical size as the 650 screen, it has a resolution of only 240 by 240, 44% lower than the 320-by-320 resolution on the Treo 650 screen.

There are some offsetting pluses. In my tests, downloading Web pages on the Treo 700w was wicked fast for a hand-held, typically hovering between 500 and 800 kilobits per second, roughly 10 times as fast as on the Treo 650. Also, the new model has more than twice as much usable memory, and slightly better claimed battery life.

Palm has also added some nice features to the Windows Mobile software. The Today page, which summarizes information like appointments and unread email, has been vastly beefed up. It now includes a box for looking up phone numbers and one for doing a Google search.

In addition, you can quickly initiate a phone call from the Today screen in a number of ways: You can start typing a number or a name from your contacts list, and that contact will pop up. You can use a previously assigned speed-dial letter or number. Or you can set up a scrolling bar containing photos of your frequent contacts and then tap on the relevant picture.

Palm has added other goodies. You can choose to respond to an incoming call with a text message, which is great if you’re in a meeting. And when listening to voice mail, you can use VCR-like icons to navigate among messages.

But lots of tasks on the Treo 700w require extra steps. On the 650, one click of a button takes you to email. On the 700w, two button presses are necessary. On the 650, the leading email programs allow you to delete a message by pressing one key. On the 700w, you have to press a key, view a menu and then press a second key.

And the email program lacks many of the advanced features of VersaMail or SnapperMail on the Palm-based Treo. For instance, there’s no simple way to delete — or to mark as read — large groups of messages.

When you’re on a phone call on a Palm-based Treo, you can turn on the speaker phone or mute the microphone by tapping large icons with your thumb. On the Windows-based Treo, you have to open a menu and then select these functions.

And then there’s that email bug. If you’re using a so-called POP email account, like the ones offered to consumers by EarthLink and many others, the Treo 700w will disconnect from the network after it checks for new email. This means that when the 700w next checks for email — or when you next try to get on the Net — you’ll have to wait for it to dial into the network again, which is annoying. Microsoft is working on a fix, but it will take months to deploy the patch to users.

The Treo 700w will appeal to some Windows Mobile fans, and to some corporate IT staffs. But for everyone else, I advise sticking with the Palm-based Treos.

• Email me at mossberg@wsj.com.

Lately, however, that has begun to change. A number of major Web-mail providers have introduced versions that offer much more of the ease of use and power of desktop email programs like Microsoft Outlook. Yet they still retain the core advantage of Web-mail services: They can be accessed from any computer, Windows or Mac, with your settings and preferences always present. All you need is an Internet connection and a Web browser.

Google kicked off the trend last year with Gmail, which for the first time offered to store, free, a huge volume of old email messages — 1 gigabyte, which was raised to 2 gigabytes or more. Other Web players boosted their free storage limits.

Now, the Web-mail competition has taken a new turn, going beyond storage. Yahoo, EarthLink and AOL all have recently introduced versions that lift their functionality well beyond the old model of Web mail. All are using new programming techniques that turn them from simple Web pages into something resembling the fluidity of desktop applications.

For instance, these new email offerings allow you to drag and drop items, and do most things without waiting for a Web page to refresh or a new page to open. That’s a big change from the old system, where any significant action was performed in circuitous ways and required the Web page containing the email program to tediously reload.

This is a major breakthrough, and one that will extend beyond Web mail. More Web sites will be revamped to look and work like regular desktop programs, hastening the day when most applications may reside online.

I’ve been comparing the new version of Yahoo Mail, which claims to be the leader in Web mail, with Gmail, the challenger Yahoo most fears. My verdict: The new Yahoo Mail is far superior to Gmail. Yahoo more closely matches the desktop experience most serious email users have come to expect. Gmail, by contrast, is quirky and limited. Its only advantage is its massive free storage, which exceeds what most people will ever need.

Both products are officially in “beta,” or test, status. Neither is easy to obtain and use. If you want a Gmail account, you have to be invited by an existing account holder, or go through an odd sign-up process using your cellphone. Yahoo’s new version, just a week old, is — for now — available only to Yahoo Mail account holders the company selected, though the user pool will be expanded later this fall.

The new Yahoo Mail retains the basic terms of the current version. You get 1 gigabyte of mail storage free of charge, and the program displays ads. For $20 a year, the storage doubles to 2 gigabytes, and the ads disappear.

The new version is radically easier to use. For example, there’s a preview pane, just as in desktop programs, that allows you to view the contents of an email without opening it. You can open multiple emails at once. You can drop messages into folders you create. You can right-click on various items to see short menus of useful tasks, like “add sender to address book.” You can delete multiple messages at once by selecting them and clicking on a trash-can icon.

By contrast, Gmail has none of these new, fluid, desktop-like features. You can’t scroll through all of your messages’ headers without loading a new Web page. And there’s no preview pane, only a feature that shows a snippet of the content of an email.

To delete groups of messages, you have to wait for multiple consecutive pages to load, showing new headers. You can’t drag and drop. And Gmail’s address book, unlike Yahoo’s, doesn’t allow you to collect contacts into group addresses.

But Gmail’s limitations go beyond this. On several key issues, Google’s engineers have decreed that familiar email practices are no longer useful, and have substituted approaches they prefer, arrogantly denying users any choice.

Gmail doesn’t allow folders, only color-coded labels, as an organizing technique. It forces you to view all of your email in groups of related messages called “conversations,” instead of viewing them individually as they arrive. Other email programs also allow such grouped views, but they permit users to choose. Not Gmail, where “option” is a term too rarely employed, except in reference to employee compensation. (Yahoo plans to add an optional grouped view soon.)

Similarly, Gmail forces you to view ads alongside your emails. Unlike Yahoo, it offers no paid option to avoid the ads.

I’m sure Gmail will get better and better, and will eventually adopt the new programming techniques that allow desktop-like ease of use. But I’m not sure Google’s arrogance will ever make room for user preferences on things like folders or ads, or how emails are grouped.

Yahoo’s new email program would blow Gmail away if it were widely released today. That’s partly due to its features, but also to its respect for user choice.

• Email me at mossberg@wsj.com