Ditto^^ The OP didn't even say that he was considering a D600 (which is a fine camera by the way), he said he was deciding between a new D800 or a D3s. If I tell someone I am buying a new car and it's between a Porsche turbo Carrera and a Ferrari California and want to know which you would choose, one normally wouldn't say "go buy a Corvette" (a fine car but not in the same league, oh, and i DIDN'T ASK ABOUT A CORVETTE!).
Okay now my rant is over....
The D800 (D800e) is a fantastic camera for landscapes, concerts and any other telephoto work. There is no better DSLR on the market for this work. You could just point in the general direction shoot in raw, and "frame up" in post. It's THAT good with all those MPs. It excels in all other categories but there are better choices if you need high FPS or magical portraits (although I have taken some portraits with the d800 that literally took my breath away). The D3s is still being touted as among the finest Portrait digital cameras Nikon ever put out, and I love mine but if I am shooting a concert or landscape, it stays in the bag most of the time. Both cameras are exemplary.
I would highly recommend the D800 based on your BRIEF description of your needs. You will be very pleased with your choice.