Hello... both those cards are not 256-bit memory... is that what you want?
Also a word from experience... get a card with a true, rear mounted, external exhaust fan... as those cards will just re-cycle the hot air into your case... increasing tempertures to the rest of your computer components.
out of those two cards I would agree with the previous two posters. looks like you get a little more bang for your buck with the eVGA.
I haven't owned an eVGA myself but I have owned GIGABYTE and haven't had an issue with their products. even have a motherboard of theirs I have used forever. I am not saying they don't have lemons but I have had good luck with them myself.
shame they don't offer an SO model for the 550Ti. GIGABYTE does those up.
if you decided to get a AMD3 motherboard instead of a 3+, then that might save you enough money to get a 560. It has almost twice the cores 192 vs 336, so substantially more performance. they are available for $180 and up.