it's never that easy to say which console will be the better one. the companies can juggle and brag with numbers as much as they want, that doesn't mean a thing.
even the impartial performance test won't give you a clear insight as to how this will play out in the future.
take processor performance e.g.: Sony seems to win this one from a brute power perspective, due to its 3.2GHz Cell processor with seven synergistic processing units, plus an eighth SPE reserved for redundancy - whatever that means.. BUT (!!!) we should realize that it's enormously difficult and time-consuming to program a game for an 8 processor console !
the Saturn console had the same problem. it was by far THE most powerful game console of its time, yet it was a flop, because it was almost impossible to program a proper game that would run on a 3 unit processor ! there were only a handfull of games for the Saturn.
now i don't think that this is going to happen to Sony. they sure will release all the promised game titles, but it might result in a higher price for the games.
the possible downside of xbox360 could be Microsoft's "all xbox live"-policy:
they've stated that EVERY single game for 360 will have a "live" feature. sounds great, but many of those games will be ESPECIALLY designed for xbox live, which might result in a crappy singleplayer-mode; and not everyone can afford a live account.
personally, i will go for the xbox360, because i already have the xbox, and i'm seriously looking forward to some of the 360 titles. and also because Sony has a long history of over-promising and under-achieving.
just my :2 cents: