PS3 would be my choice... and I wouldn't regret it.
When sony first came out with the PlayStation, it revolutionized the way people played video games. I've been a big fan of Sony, the PS1, the PS2, PSP, and all the games + accessories that come with them (ie. Time crisis 1,2 & 3)
I stand by Sony, and nothing will ever make me regret it or look back.
And for the whole X-Box/X-Box360 having Halo+Halo2, I can always go over to my friends house to play it. (Since thats the only good game for that console{In my opinion})