Questions on upgrading memory

I’m looking at moving up from 512 mb to 2g of ram. I’ve got it narrowed down to coursir brand, but I’m not sure what the difference is between these two makes.

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=80097-55

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=80097-41

I know that 3200 is as high you can go unless you want to overclock your computer now, so I don’t think I’m going to go higher than that.

The first set has faster verified timings (2-3-3-6) than the second set (3-4-4-8). It makes little difference in practice, from most benchmarks I’ve seen.