I also came from HTC and was in this same predicament. I ultimately chose the SGS3 but you have no idea how close I was to choosing the HOX. Either way I feel I would have been happy.
I agree that if you're used to Sense, you'll probably not like Touchwiz. Not a problem for me, I rooted the day after I bought the phone, now I run either Jellybean AOKP or CM10.
The screen on the One X is amazing, I'll just put that out there. If you look closely it's easy to see the pixels (or rather, sub pixels due to pentile arrangement) on the SGS3, not so with the HOX, also the maximum brightness is worlds brighter, makes a big difference if you're outside on a nice day.
Exterior design is kind of a tossup. The SGS3 looks better in person than it did online for me. I thought it would be piss ugly in person (not rectangular, not all that symmetrical vertically, etc.) but it's actually quite nice in hand. I would still probably prefer the white HOX, but just by a hair.
In terms of smoothness they should be almost exactly the same due to hardware. But Sense, even Sense 4.0, which is lightened, is a CPU/memory hog, so it bogs down a bit more from my experience and others experience. You can get around this by rooting, but if you're on AT&T, you'll likely have update 2.20, which hackers haven't found a way to root even after about 1.5 months of hard work. HTC doesn't have the kind of money Samsung does to throw around to make carriers more compliant, so, locked bootloader+s-on=hard to root.
If you want expandable storage/removeable battery then SGS3 is kind of a no brainer unless you hate touchwiz/love sense. I feel that the differences in screen quality and exterior design aren't enough to make up for the difference.
Me personally? I really wanted to go with the HTC One X. To be honest if the development community on the HOXL was running along a little better I probably would have. Battery and expandable storage were never issues for me. However after rooting I can't go back. Touchwiz was worse than Sense for me, but custom ROMs>>>>all manufacturer skins.
Oh, and for waiting for next batch? If you're from the Hero you've waited plenty long to see a drastic improvement. I sort of doubt that there will be any game changers out there this year unless you count the iPhone 5, but if you're on this forum you probably don't consider it too seriously. Otherwise there's the Note 2 and new Nexus phone(s). If you like massive screen phablets, then sure maybe wait for the Note 2. Nexus is nice but honestly I don't think it's going to be as much of a leap as it was last year with the Galaxy Nexus. JellyBean just came out, so no new version of android coming out with new nexus (at least I doubt it), I bet the hardware in the new Nexus will probably be in a similar tier of performance to the HOX and SGS3. If you know how to root your phone then not having stock android isn't a real problem either.
