Quicktime 7+ is H.264
H.264 is good quality but watching it, it sucks lots of CPU power someone on a slower processor would have issues watching.

And encoding anything larger than 320x240 in H.264 can be slow unless you have a server farm stashed in the basement.

You'll have to play a lot till you get a result you like though, at least I had to.

And Vegas in general is so painfully slow which ends up in a nicer looking video but damn