Please remember that any mention of competitors, hinting at competitors or offering to provide details of competitors will result in an account suspension. The full rules can be found under the 'Terms and Rules' link in the bottom right corner of your screen. Just don't mention competitors in any way, shape or form and you'll be OK.
a lot of games will need the extra vram nowadays so deffo the 6950.
only problem with ati (i came from nvidia to 2x 6950s) is their terrible drivers.
1GB will be absolutely fine.
1 gb is fine. You may not get the absolute best settings but for the majority of games, 1gb is easily enough.
Just a few that use more but that doesn't matter so much if you turn the AA and AF down a notch or two.