Upgrade advice, GTX

[Reaper leader]

Hi all need a little help, I don't know which one to go for, for CLOD of the following 2:

1: The faster, Gigabyte GTX 580 SOC 1536MB or
2: The slower but twice the memory, Gigabyte GeForce GTX 580 3072MB ?

Both second hand but still with warranty and about same price.

Any ideas ?

Regards

[Flanker35M]

S!

Have you compared the price to the 670GTX? Fast and has 2Gb memory on it. But if want 580GTX I would take the 3Gb version.