Which one is better.

Ackbarr

Intel® Pentium® E6500 2,93 GHz
Intel® G41/ICH7
2x2 GB DDR2 800 MHz
ATI Radeon™ HD5550 1GB
640 GB
Midi tower, 350 W
DVD±RW Dual Layer

or

Intel® Pentium® E5400 2,7 GHz
Intel® G41/ICH7
2x2 GB DDR2 800 MHz
nVIDIA® GeForce® GT220 1GB
500 GB
Midi tower, 300 W
DVD±RW Dual Layer

And how much FPS I will have in 8v8?

Enairgized

I prefer the 2nd model since it's graphics card is nVidia. ATI is also good but not as good as GeForce.
The difference between 2,93 Ghz and 2,7 Ghz isn't noticeable.
Other hardware is the same.
My hard disk is no problem. Mine is 1 TB and I got only 206 Gb of it filled.