I hv xbox360 arcade(with 60gb hd extension),but am planning to get ps3(dont know when),because developers has just started to realize the potential of ps3.So if you're expecting good rpg/action games in the future then i'd suggest you get a ps3.Most of them revised the 360 games for ps3 with added features and graphic enhancement.
And yes,you need good hdtv to play 360 or ps3.It is still possible though if you use the ol tivo.
You also have to be aware of the risk of getting RROD(red ring of death) on xbox360..