I like the Corsair for its power but the Cooler Master for its modularity. They're both 80% certified and they both have a single +12v rail.
Personally, I would take the Cooler Master because it's modular, however, if I had plans to build a rediculous computer with SLI GTX280s and an i7, then I would take the Corsair.
This isn't my power supply though, it's yours. You must answer these questions to yourself:
Do I care about cable management much?
If I do, does my case allow me to tuck all those unused power snakes somewhere out of the way?
Am I going to build a really powerful computer with this power supply in the future?
Why won't you buy anything used? For the most part, people in the B/S/T forum won't try to screw you by selling you a defective item, and prices are lower than stuff found on Ebay. A lot of people who use the B/S/T forum are already well-established in the community. I would be wary of people that don't have many posts and havn't been here for a long time though, but as I said earlier most people have been here a while. I've had 7 transactions here, one in progress right now, all with different people and I havn't had any problems.