It's very close. As one who chooses to stay as neutral as possible, in order to enjoy a variety of brands and platforms. I remain quite open minded.
I've found just when you think you know a brand well, something changes.
Here's an example. I've had about 8 HTC Android smartphones since they began bringing them into the US. Overall I liked the build quality, but found the UI only average at best.
During this period I also tried 7 Samsung phones, which initially weren't the best when it came to call quality. However as time went by and I upgraded as new models were released, they improved significantly.
The introduction of the Galaxy line was a big improvement. The UI is quite good especially on my new S III. Despite all the complaints about how thin the battery door is, it's made out of a very high quality material, has a very well designed, secure closure, so once it's in place there's no creaking or noise that tends to be heard from other phones with battery doors. This is a point that many use to bash the phone about, however I find the high quality plastic case very well done. It feels very nice in hand. Why people complain about it being light, is again, just an excuse to complain.
If I had to choose between the two, the big deciding factor is the SWYPE keyboard. First introduced in the Galaxy S, all Galaxy models come with it, and I've been using it for three years. It's the fastest, most enjoyable input system I've ever used on a touch screen phone. It's so much better than typing on glass, you simply have to experience it for yourself.
SWYPE submitted the software to Apple for consideration (not as an app) , but Apple rejected it. I believe it's because Apple felt threatened by how good and efficient it is. Since Apple didn't invent it, they weren't about to pay to use it.
Once you've used it you'll understand. It's likely that Apple tried to low ball them on the price, and when SWYPE wouldn't cave in to Apple, it got rejected. I cannot imagine any other reason Apple wouldn't want to have it. Many of my friends use Samsungs just because of SWYPE, even though they enjoyed their iPhones prior to switching to Android, Samsung and SWYPE.
So for me, the number one advantage of the Samsung Galaxy Line is SWYPE. I can swype out an email in half the time as compared to an average keyboard like Apple uses on iPhone, and I'm pretty fast on the iPhone keyboard.
Finally they're so close it, comes down to personal preference. Performance is nearly equal, the lack of an expansion card in a negative for HTC. Beyond that you may want to plan on spending some time in an AT&T store trying one that has been activated.
http://www.swype.com/
Hope this helps
Thank you. I am in the same boat at the OP....want to wait and see what the new iphone will bring, I have a 4S right now, so if it isn't that big of an upgrade i'll just go android