For event coverage, the D3s is the better camera. The D800 has 36mp files, and doesn't have the same speed that will help you grab as many frames as you need. You'll also blow through memory in terms of both cards and hard-drives in a very short time. It's also advisable to have a very powerful computer if you are going to be doing any CPU intensive processing of that large of a file.
The D600 is a great camera, similar in low light to the D3 or maybe D3s, though the grain is finer. Also great for landscapes, as the dynamic range is incredible. Though, it doesn't have the speed you'd be looking for if you were shooting events (buffer fills in only 15 shots). They are still large files, but not on the same level as the D600.
If you were doing only landscapes, the D800 would be the perfect camera. If you are doing both events and landscapes, the D600 is probably a nice compromise if you aren't shooting like crazy.