I spent hours looking and researching both phones. Always been partial to HTC/sense. It was a tough call. Wanted both, but in the end I picked the S3.
In-call volume/speaker volume/call quality much better on the S3. That is a huge advantage. Even tho more and more people seem to care less about the calling aspect of smart phones today, I am the complete opposite. My first priority is how well a phone handles being a phone.
s/d card, removable battery are a plus. 2GB ram, definite plus. Sense vs TW, it's a toss-up imo. Screen quality, slight edge to the hox. Not enough to sway me. wifi on the S3 is excellent. New features on the S3 not on the hox, a plus.
In hand feel, S3 feels equally as good as the hox. Reception on the S3 is excellent.
The hox is a nice phone and it was a tough decision, but the S3 won out. No regrets, so far.
I've made comments about Samsungs build quality, but the S3 has changed my mind.