For those who may come here that are still on the fence on which device to grab, I am fortunate enough to have both: I use the "S", my Wife the Titan. And here is a list for your consideration: I will list the characteristic, and each devices performance in my opinion.
Screen: The S is just a vibrant, amazing screen. You would expect this from Samsung. The live tiles explode off the screen, and do a great job of presentations. The Titan is just exceptional for Movie watching and is no slouch. I prefer the "S", but in all fairness this is a push due to personal preference.
Response: The S is just seamless. Whether scrolling, changing screens, loading up pages, running apps, there has been no hesitation in the least. The Titan is great, but my Wife and I both have seen the Titan lagging behind the "S" when we load up similar commands, and this is in spite of a slightly larger processor. Score this one for the "S".
Camera: Not even close. The Titans reproduction, shutter speed, extras, modes and editing is all superior to the "S".
Call Quality: Neither is bad, but the "S" is clearer.
Reception: Actually, the Titan has better bars and reception. The "S" doesn't drop anything, but the Titan is stronger.
HUBs: HTC is much more polished than the Samsung offering. I just deleted the Samsung Hub, my wife still uses the HTC.
Build: I love my "S". It is solid and the backing gives it a better grip than the Titan. But that aluminum build is great.
Size: Umm, it is called the Titan. Duh.