Vote for VGA /need help

Hi all, I think about new graphic card for GPU Cycles rendering /is possble to buy serious Octane licence/ , but I need to know, what type of card is good for my business… I think about GeForce GIGABYTE N56GSO-1GI Super Overclock or ASUS ENGTX560 Ti DCII/2DI/1GD5 , but its about 40Eur more expensive… this cards have very similar frequency, but ASUS 560Ti have 40 cuda cores more… Its a big difference in render time? Thanks for your tips and replys…