Let me see if I can think how you think...
Any little extra fps that draws nearer the chance of predicting Mr.X's trajectory for a long deflection shot is worth its weight in gold, right?
LOL!
The 2Gb VRAM is going to give you a lot more eye candy without any impact on the fps (the fps practicaly halves when your VRAM reached its capacity and your GPU starts swapping data from the main memory or, even worse, the hard disk...). That is good!
But you need more for what you have in mind!
Since you commited the money, pay the additional 30 and get the good version of the 560ti. I have read in some reviews that the new version is very near to the performance of the GTX570.
So my comment, pay and get the good one.
~S~
PS. I solved my problem otherwise; I fly blue so I do not have to fly against Kosedub
ROFL!