Omega tends to lag behind a bit on the Nvidia drivers. I'm not sure why, if they are more difficult or what. Thats always been the case. However, when he does put one out it's usually worth the wait.
Driver Heaven puts out their Zeropoint drivers far more frequently, but they rely on gamers to point out bugs for them to fix too. Optimizations are usually similar to the Omega ones. Its just a tradeoff. With one you have to wait forever for updated drivers, but know they will almost be guaranteed to be stable and work right; with the other you get more frequent updates but have to deal with more bugs along the development path.