Usually I say Yes. You can't tell from looking at one thing which of two different cards will provide better frame rates. Think of a CPU. Which would you rather have, a CPU with a 2.6GHz clock rate or 2MB L2 cache? You really have no idea which would be better.
In this specific case I'd say get the 2GB cards if they are the same price as the 1GB. You can always OC cards and get more clock speed, you can't add ram to the cards. And the less then 80MHz difference between the two shouldn't be much.
Thanks for the feedback, greatly appreciated