Which one is better in term of performance? 2 GC vs 1 GC (high end, memory)

[schwan]

Is it wiser to run 2 x $200 Graphic Card or 1 $400 GC?

[Skunk Workz]

This will depend upon the cards more than price, and will vary depending upon what you are using them for, but a single high end card should outperform two low end (or older) cards.

[Peregrine]

What he said.

Also the inverse, 2 new high end cards will outperform one.
Generally speaking.

[LeaderOCola]

depends how much memory each GPU core needs.