GTX 560 Ti 448 cores (4th link) is on par with HD 7850 (second link). It's up to personal preference after that point. I'd get the GTX card due to technologies like PhysX and adaptive Vsync. Make sure you have a proper power supply unit, though!
yeah that to, nvidia techs are great, also the xfx (2d link) has far cry 3 free :P and 2gb of vram. (even when i rather nvidia over AMD).
Yeah it would be between the EVGA and the XFX, would depend on the rest of your system specs tho. If you've got support for pcie 3.0 definitely go for XFX 7850, extra mem and bandwidth would be stellar
PCIe 3.0 has no performance impact at all.
Ok thanks is thaere any other things that can he'llp me decide between the 2