The Panny and the Sammy are both really good. I'm not as impressed by the Philips sets I've seen, but they aren't awful or anything.
It's really up to you to go and view the sets extensively and decide for yourself. Panny plasmas and Samsung LCDs have different 'kinds' of pictures, one isn't necessarily hugely better than the other, some of it is personal preference.
The Panny plasmas I've seen seem (to me) to be a tiny bit dim, and a tiny bit soft. But they also have a very 'natural' looking picture (some would call it 'accurate'), and seem to excel at making Blu-Ray movies look a lot like what they did in the movie theatre.
Samsung LCDs, on the other hand, seem to have superior brightness and sharpness... a very punchy, 'wow' sort of picture, almost better-than-real (especially in the A650 models... your A630 is toned down slightly due to the non-glossy screen). But some ppl don't like 'better than real', to them it looks unnatural.
You're really going to have to view the sets a LOT for yourself, and come to your own decision regarding stuff like that.
Oh, and if you're going to game on the plasma, might want to read up on burn-in issues. They can be avoided, but it's best to know what's up.