obviously the 5970 is faster than a 7750.
its not the generation of 5xxx vs 7xxx, its pure transistor at play. 4.3 billion for the 5970 whereas the 7750 has a mere 1.5 billion.
so even though 7750 has a better architecture, the 5970 will beat it at processing power.
its not wise to compare them. anyway, @shreeaux, thats a bad point of presentation, that image.
and dont get the 5750. thats an old fart of a gpu and can go kaput at anytime. better invest ~8-10K in a 7770/7790. you will get better, architecture, lower power consumption, and more importantly, 3 years of warranty.
cheers!