If you really think Sony's online compartment will be equal or better, remember this...1) Sony has already stated that it's still left to game developer to implement online solutions for their games, and 2) This is MS's second complete go at online which means a ton in the development area. It takes time to implement a program like that and it's just not something Sony will be able to equal. Absolutely no way they can match it.
The hardware of the two will be very similar and most games will be almost identical. I like the online aspect of the 360 a lot. I like the few extra developers Sony has. I also like the fact PS3 is a BluRay player, but that is going to cost you significantly when it comes out. It will never be equal or less than the 360 when it comes to price.
I'm all for buying both. What I'm really getting at is there are reasons to own both which some might overlook. Still, most people don't play online and waiting might be a good idea. But if all games look fairly similar and you have the 360 at $100+ cheaper, you might want to rethink the choice if you're only getting one.