Which would you pick/recommend for an all purpose machine?
in most cases your better off with a single card even if it is slightley less powerfull than 2 in SLI you won't have headaches of scaling, cooling as the cards would be right on top of each other and im guessing one 690 would use a lot less power than two 680's as well
The two 680s look like they are more power hungry by a little bit and are marginally faster. They would also take up a minium of 4 slots since its a two slot design for a 680 generally. 690 also runs a little cooler and a little less noise. The 690 also looks really nice. So really the 690 wins inless you need more ram since it only has 2gb per gpu on the card.
http://www.anandtech.com/bench/Product/585?vs=586
It is still two 680s in SLI they are just on the same card, scaling is still the same.
Also @OP the 680s if you're going to OC 690 if not.
If you have the money, two 680s in SLI, however one 690 is incredibly powerful, and would use less power. It is also cheaper than two 680s. I would personally go with a 690. Two 680s will get hot and coolling them will be a real difficult challenge.
- Less power, less heat, Single card and its a beast.