The X7501 is a master of all wireless networks, covering HSDPA/UMTS high-speed 3G and GSM/GPRS/EDGE cellular networks, as well as 802.11b/g Wi-Fi, GPS, and Bluetooth 2.0. The device is sold unlocked, so all you need to do is get a SIM card from a wireless operator, slide it into an easily accessible hatch on the side of the phone, and power up. (HTC seems to have built the X7501 in anticipation of frequent SIM changes.) The GPS feature, paired with TeleNav's GPS Navigator, turns the X7501 into a terrific, turn-by-turn navigation system with a gigantic display and clear-spoken directions. It works with other GPS-enabled apps, too, but TeleNav's solution on this big screen turned out to be a real mind-blower.

This device uses a magnet to attach the removable keyboard to the display. The magnet is effectively the entire keyboard. If you stick this keyboard to your fridge, you'll have a hard time getting it off. It will wipe out the mag stripes on your credit cards. Fortunately, the X7501's carrying case is shielded to reduce the magnet's strength to a level comparable to the Mag Safe power connector on a MacBook Pro. I have had my wallet next to the X7501, while in its case, without incident.

The HTC Advantage X7501 is the best that Windows Mobile 6 Professional has to offer, at least among the devices that I've seen to date. True, it is too big for a pocket or a belt clip, but it's about the size of a Day-Timer, and everyone was okay with that. The screen is big enough for handwritten notes, and could well obviate the need for a paper pad. I've found room for the X7501 in my working life, and while it would never be the only phone I'd carry, I wouldn't feel lost if, for a short trip, I brought this machine instead of my Mac notebook.

The AT&T 8525 (also known by manufacturer HTC's model name "Hermes") was the second device I received for this review and the first Windows Mobile phone I had seen in a couple of years. Running the 8525 and Windows Mobile 5, I discovered what became of the Pocket PC, and I was impressed. Then I received the T-Mobile Wing, and I discovered where the Pocket PC is heading now that Windows Mobile 6 Professional is the standard: eBay. And I felt a bit silly for being impressed with the 8525. We evolve.

AT&T's 8525 is enormously popular as a hacker's toy. It is quite fast for a Windows Mobile device, and it can be overclocked to run even faster. Even though AT&T hasn't released the free promised upgrade to Windows Mobile 6 Professional, there are lots of 8525 owners running Windows Mobile 6. Putting WM6 on Hermes was a worldwide cause before iPhone begged to be cracked, and various leaked and concocted WM6 firmware upgrades for Hermes abound. Windows Mobile platform hacking is fun, and the AT&T 8525 is great for it.

None of that does you much good as you shop for Mobile Professional phones. The AT&T 8525 is a nice handset if it's your first brush with Windows Mobile. After being tweaked with some freeware, it plays many types of video clips smoothly. It performs marvelously on AT&T's 3G network, and it's even more impressive on a Wi-Fi LAN. The two-megapixel camera has a light, along with a switch that enables macro focus, unique among devices reviewed here. The display is clear and it responds well to stylus and finger pressure.

That's pretty much where the AT&T 8525's charms end. We all love speed, but it comes at the cost of battery life, and where this handset is concerned, you have to trade speed for looks. I'd rather have a good-looking, slower phone with a longer battery life (T-Mobile Wing) than an ugly, faster phone with a shorter battery life (AT&T 8525). The 8525 is a contourless brick, uncomfortable to hold to the ear and unsightly in a pocket. There are too many controls around the edge of the phone, and they are poorly positioned and faintly labeled. I had to take the phone down from my face to look at the buttons, and that's a show-stopper for me. Also, I never found a good way to carry the 8525 other than in the pocket of my notebook bag.

It's not that the AT&T 8525 is a bad phone; it's just not good enough to justify the extra bulk and the user-unfriendly, throwback exterior design -- not when there are so many good and good-looking handsets on the market.