If you're in the US:
Obviously the SGS3 is a solid choice on every carrier. It doesn't have the best screen, and it may be too big for you, but it's packed with features, has a full-day battery life (and you can replace the battery, too! Another thing your iPhone couldn't do), and has a physical home button, which may help you feel "at home" (no pun intended). Otherwise, here are your other best bets:
Verizon:
- Motorola Droid RAZR M if you don't want a big phone (and it's getting Jelly Bean before 2013)
- Motorola Droid RAZR HD if you want a big screen and can wait (also getting Jelly Bean soon)
- Moto Droid RAZR MAXX for the same thing, but a bigger battery and more internal storage
- Galaxy Nexus...with an asterisk. Some people will tell you that it's not a real Nexus because Verizon can delay updates for months (the Jelly Bean update took about 2 months). However, it isn't an issue if you're into jailbreaking (we call it rooting here on the Android side); you may have to wait a couple days tops. You do get 32 GB of onboard storage, though.
- What I would get: Droid RAZR HD.
AT&T:
- HTC One X if you want a big, powerful phone with the best screen on the planet (and are OK with 16 GB of non-expandable storage and slightly questionable battery life)...right now
- HTC One X+ if you want a big, even more powerful phone with the same amazing screen, what should be a full-day battery life and 64 GB of storage...and can wait for it to come out
- Unlocked Galaxy Nexus from the Google Play Store if you want fast updates, pure Android, areasonable screen size (with on-screen buttons, 4.65" feels more like 4.3"), and can sacrifice camera quality, 4G LTE, and anything more than 16 GB of storage...and need it right now
- Samsung Galaxy Note and Galaxy Note II are really big phones. People call them "phablets," they're so big. With a bigger screen comes added functionally, but you can't use either with one hand. They're both pretty fast, though (obviously the Note II is faster). I'm not sure if the Galaxy Note II is coming to AT&T, but it would make sense, since they were the only one with the first Note for a long time (until T-Mobile got it). The Note II is still international-only right now. I'm not sure if I would recommend these phones to an iPhone user, but it's there.
- Unlocked "Next Nexus": a device that's been rumored, but we know nothing for sure about it, except that it's better than the Galaxy Nexus. No one knows how long you'll have to wait for Google to release it, though.
- LG Optimus G: I'm not very familiar with this one, but LG's best handset will arrive AT&T soon. If you can wait till it comes out, it's one you should consider. Read Phil Nickinson's thoughts on it here
http://androidcentral.com/lg-optimus-g-hands-g-style, here
http://androidcentral.com/hands-video-optimus-g, here
http://androidcentral.com/device/lg-optimus-g, and here
http://androidcentral.com/tags/lg-optimus-g.
- What I would get: wait for the next Nexus and decide between that and the One X+.
Sprint:
- HTC EVO 4G LTE: (my phone!) what some people say the AT&T One X should have been. Everything's the same, except HTC redesigned the exterior and added a microSD card slot (to complement the 16 GB of storage), a kickstand (that supports two orientations well and a third, portrait orientation if you can get the balance right--I find that I have to turn it around on the table, etc., for it to work), a physical camera button, and, perhaps most importantly, a slightly bigger battery (2000 mAh vs. 1800 in the One X; One X+ has 2100 mAh). Same amazing screen (though, again, you might find it to be too big), same great camera, and same HTC Sense UI, with its great added features (I love 'em) and poor multitasking (I tolerate it). You may not notice it, but lots of people, including me, do. All around a great phone.
- Galaxy Nexus, again with an asterisk. Updates are controlled by Sprint, not Google. That being said, Sprint is usually better about updates than Verizon. The update to Jelly Bean took Sprint about 1.5 months and Verizon about 2. 32 GB of storage (up from 16 on the GSM unlocked version) and some rooting action may console you, though.
- Motorola Photon Q has a great slider keyboard, and the screen isn't too big. It's also Motorola, which Google now owns, so maybe it will see faster updates than phones from other manufacturers (then again, no guarantees). Probably your best bet if you want a slightly smaller screen and a better camera than the Galaxy Nexus, and it's your only option if you want a physical keyboard, though I doubt that's a priority for an iPhone user like yourself.
- Samsung Galaxy S II, Epic 4G Touch is your only good option if you want Sprint's old 4G WiMAX network. The only thing wrong with the phone itself is that it's a year old. That said, if you live in an area of strong WiMAX coverage and don't think you'll get LTE within a year's time (half of your contract), maybe WiMAX is the way you should go. However, I would discourage this. The places Sprint chose to put LTE first are probably the same places for which they did WiMAX. Think twice, no, three times before you get this phone over an LTE-capable phone.
- LG Optimus G is also coming to Sprint with a 13 megapixel camera on the back. (AT&T's version is 8 MP.) Otherwise, it's the exact same thing, but on Sprint's CDMA-based network instead of AT&T's GSM-based network.
- Maybe the next Nexus or an updated version of the HTC EVO LTE (a la One X+), but I wouldn't bet on it.
- What I would buy: HTC EVO LTE. I bought it a couple months ago, and I'm loving it overall.
T-Mobile (not likely, but I'll go ahead anyway):
- Galaxy Nexus (unlocked) is even better here because T-Mobile gives you better speeds sans LTE with their HSPA+ network that's almost as fast as LTE in some places.
- HTC One S gives you impressive speed and great build quality in a smaller package. The screen isn't as great as that of the One X, One X+, and EVO LTE, but the lower pixel count makes the phone run faster. HTC's promised an upgrade to Jelly Bean for this guy, too. Still stuck with 16 GB of internal storage that's not expandable, though. Camera is the same as the One X, i.e. awesome.
- Samsung Galaxy Note or Galaxy Note II: see above. We're pretty sure the Note II is coming to T-Mobile; see here
http://androidcentral.com/what-t-mobile-branded-galaxy-note-2-will-look
- Next Nexus--see above
- HTC One X or One X+ (RUMORED): T-Mobile may get either of these two phones (getting both is unlikely but still possible) sometime later. I don't recommend betting on it.
If you're in the UK or a similar market, you should really only consider 6 phones:
- Galaxy Nexus...but the camera sucks
- Next Nexus, but we know very little about it, including when it will come out
- Samsung Galaxy S III
- HTC One X+ is probably well worth the wait (compared to the One X)
- LG Optimus G, but availability may vary. Something of a dark horse.
- Samsung Galaxy Note II, with the same caveats as earlier
I don't know much about other markets, but that should hopefully give you lots of help. Sorry for the book, but this shows a great thing about Android: lots of choices. It can get confusing to some people, but it makes the phone you get more personalized.
Sent from my EVO using Android Central Forums