Full cover heatsink or seperate heatsinks.

Full-coverage are hard mounted and don't fall off.

The GTX280 has RAM on both sides plus the NF200 chip and MOSFETs. You're looking at 20+ RAMsinks.

I would just get the full-coverage block. Just a note though, the Swiftech block is missing a contact point on one of the MOSFETs. Just add a piece of thermal tape to account for this.

The full cover heatsink would most likely cool better, given that it has a greater surface area.

Thought the RAM will have it's own limits before the heat will be the limiting factor.

Your Swiftech MC14 heatsinks aren't "Crappy." I wouldn't spend the money on that full cover heatsink, but you will have to get 8 more ramsinks for the memory on the back of the GTX 280

Edit: DuckieHo is right, you'll probably have 20+ heatsinks on there if you were to use them.

I use those Swifty sinks on my vRAM. If you mix a little AS5 and Arctic Silver Thermal Adhesive they stick just fine!

Full-cover heatsinks kinda worries me because all the RAM chips may not be making adeqaute contact if you use TIM. I'd find some thermal padding to use with it (if it doesn't come with it).