GTX275 was a very good card back in its day, now its old, outdated...
Radeon HD 7570 is a newer model, unfortunately it's also a low end, mid class at best.
Like others said, get one of the new GTX600 series, best value vs performance is GTX660 Ti ($280 - $300), best overall is GTX680 ($480 to $550). Cheapest and also good would be a GTX650 Ti ($130-$140). For both GTX650 and GTX660 get the Ti version, much better than the non-Ti for only about $20-$40 more. Best brands are EVGA, ZOTAC and MSI Frozr.
From the Radeon HD cards, at least an HD 7770 or 7850 would be good enough. Any of of the HD 7900 series are very good. Best brands are XFX and Sapphire.
Personally, I prefer nVidia GTX over Radeon HD, due to better specs and proprietary nVidia stuff like Physics, 3D, etc.
Out of the two cards in your question, GTX275 is slightly better.
HD 7570 has low 978 benchmark score:
http://www.videocardbenchmark.net/gpu.php?gpu=Radeon+HD+7570&id=90
GTX275 has 1234 benchmark score, also low:
http://www.videocardbenchmark.net/gpu.php?gpu=GeForce+GTX+275&id=21
For good gaming performance, you would need a graphics card with an 1800 score or higher, like at least a GTX550 Ti, score of 1929:
http://www.videocardbenchmark.net/gpu.php?gpu=GeForce+GTX+550+Ti&id=16