Early models of the Evga card overheated, there was a pretty large outcry about it. If you are overclocking the 8800GT I highly recommend you
a) Get a aftermarket cooler
b) Buy a card without the reference cooler. It's the cooler that both these card have.
Yes, overclocking GPU's are extremely easy and I would never buy a GPU overclocked unless it was the same price as the version at stock.