If you're going sprint, get the Samsung Galaxy S2 (Or as it's known on Sprint, the Epic Touch). Seriously, it's one of the best phones on the market period, and has an amazing camera. It'll even be cheaper than the iPhone 4S ($200, there are no "bigger" options, because it takes microSD).
Also, Voice Recognition has been a staple of Android phones for over a year now. While it's not quite as feature-filled as Siri's supposedly is (still need to get individual reviews on accuracy for it and limitations), it does do most things:
1. Make phone calls, both to numbers, contacts, and even businesses. It will reference Google's system for businesses to obtain said business numbers and call the closest one.
2. Set the Alarm clock (some phones have problems, like HTC, which remove this for their own alarm clocks).
3. Send a text message, completely with voice (name, message, punctuation, etc).
4. Send an email similarly.
5. Play a song, artist, or album on any music app on your phone (Spotify, Pandora, local music player, etc).
6. Bring up a map of a location, or get a route to it.
7. Navigate to a location. It will navigate to a contact, business, landmark, or address. This is similar to the map, except it launches Google Navigation for turn-by-turn directions as you go. Like a standard GPS app.
8. Go to a website
9. Write a note to yourself
10. Do a google search
While it doesn't integrate Wolfram Alpha directly or anything, this covers so much functionality that basically iPhone is just playing catch up. And as long as there's not other people talking over you, it's pretty crazy accurate, and learns as you use it. Note that it also adds voice to text functionality, so you can simply avoid using the keyboard if you want to.
Android can do that, actually, and has been able to for a while now especially with third party apps.