The notion that the PS3 has more momentum then the 360 when they are selling at nearly the same rate for the last 3 months is a rather strange one. If you want to use the the textbook definition of momentum then by selling at the same rate they are actually carrying the same momentum. If you want to stretch the definition to actually mean a larger positive change in momentum you can't even say that right now with the sales actually down. I said back in January that this sales level was likely to be a new baseline for the PS3 and I was right about that much, at least. My initial expectation that sales were going to start to take off from there was overly optimistic, though. What I thought might become a surge actually turned out to be a bump and a new plateau. That is all the PS3 got so far from the combined effect of a major price drop and BR having increased relevance as the undisputed HD Disc format. A bit underwhelming, really, when you look at it that way.
@ShaidarHaran
Regarding Live!: I could spend $45 on a game or I could spend $45 for 13 months (Live! card that I bought from Amazon) of a service that is going to provide a significant value-add in almost every game I buy. Easy choice. Until a free service provides the same or even a comparable amount of added value to its games and the platform that runs them that Xbox Live! provides then I will continue to say you get what you pay for.
And people have been saying, "wait until game XXX comes out, then the PS3 sales will start to take off" for well over a year now. The game keeps changing, but the result (actually non-result) stays the same. IMO, both PS3 and 360 are just too expensive for people to be making purchasing decisions based on a single title, no matter how good that title may be. In contrast, at its much lower price point you have people buying PS2s just to play GHIII.
Edit: Just to clarify, I'm not saying single titles can/will have no effect. Just that they don't seem to have a sustained effect. They are just good for a spike here and there.