[Windows Phone 7 General] OGCF:
To the OP:

The first thing to do before even considering a WP7 device is to go to AT&T or T-Mobile and get your hands on them. WP7 is great, but it might not be for everyone and your own personal taste might favor the iPhone.

After doing that, here's a comparison from someone who owns an iOS device and a WP7 device:

WP7 advantages over iOS

- An all-around better looking OS. WP7 has a really unique style and that actually plays a really big role in how you interact with it. It's hard to describe, but get your hands on one for 10 minutes and you'll get what I mean. A big improvement over the 'grid of apps'.

- Zune + Zune Pass = great and cheap combo for music

- Hubs. So far they're not reaching their maximum potential, but the People Hub is probably the best right now and its a much better experience than using a dedicated app. It doesn't have all of the features of a standalone Facebook app, but it does enough so you don't have to use it as much.

- Games! WP7 may not have as many games as iOS yet, but Microsoft is supporting games waaaay better than Apple. XBL games have achievements which is pretty cool if you or your friends use a 360. There's also a bunch of awesome free games on WP7 that make some XBL games look like **** in comparison.

- Options with hardware. Don't want to get a touchscreen-only phone? Get a Dell Venue Pro with a sliding vertical keyboard or a HTC Surround with a slide-out speaker and stand. If you want something bigger you can get the 4.3-inch HD7 or the 4" Focus. There's a lot more options with hardware if you don't want to use a 3.5" touchscreen phone anymore.

iOS advantages over WP7

- The Marketplace is growing really quickly, but its a fact that iOS has the most apps and the most support of any mobile system. "There's an app for that" can apply to almost anything now.

- iTunes. Zune with Zune Pass is cheaper, but iTunes obviously has a bigger selection and usually gets new songs much faster than Zune for some reason.

- Multitasking. MS is gonna get WP7 a multitasker soon, but Apple has it now and they've done it in a really easy way compared to others.

- Web browsing. Safari is still probably the best mobile browser so far. WP7 is fast, but there are a lot of pages that don't render properly and show weird font sizes that change after each paragraph.

- Better apps. Not only does iOS have the most apps right now, they also have probably the highest quality apps I've ever used. Very rarely do I find apps that are slow or laggy compared to WP7 where about half of the apps I consider 'good' still have lag. Also iOS apps are usually more feature-packed because they've been in development for much longer than their WP7 alternatives.

- Better hardware. Say what you will about the 'antennagate', but Apple still makes drop dead sexy hardware thats way better than what LG, Samsung, or HTC offer here in the States. The Dell Venue Pro is probably the only one that can compete in overall quality but its thicker and heavier because of the keyboard and curved glass so its still Apple's win. I like my Samsung Focus but its a little too plasticky to feel like a high quality phone.

Overall:

You should probably stick with the iPhone if you want to have almost any single app you want and have a more popular ecosystem. But if you're willing to invest with WP7 it's already really good and its only going to get better from here.