Honestly, I just switched from the i9000 to the Sensation XE recently, and you'd be crazy to buy a Samsung. Nothing on the i9000 worked properly, and one thing I learnt from the experience is that because Samsung develops a wide range of electronics, they will select inhouse electronics which clearly aren't designed well, over competitors whenever possible. (Just a short list, it was incredibly laggy, GPS was useless, their OS used too much ram, and the system reserved too much ram, and there wasn't near enough to actually use the phone without it crashing, it would crash regularly when browsing, etc). Oh, and then my flash memory died (like every other i9000's, and the flash seems to be a Samsung component).
That isn't likely to change. I now own a Sensation XE, and the only problem is occasionally reception. Just remember that the main problems with the Galaxy i9000s weren't immediately evident. HTC might be the better choice, because, HTC isn't a hardware company, so isn't forced to use controllers which are crap (ie, ones designed possibly designed inhouse) simply to avoid embarrassment.
Honestly, with the i9000's, there should be a class action lawsuit. The only good thing about them is that they were unbreakable
I only had GPS lock problem which was a design bug, but easy be solved (thxs XDA).
