Need a new lens 18-200 sigma or 18-135 nikon

I want a lens that has close up and some reach. I will use it for parties, walking around, and wakeboarding. The bottom line I really want the Nikkor 18-200mm but i can't afford it.

Next choice is either the nikon 18-135 or a sigma 18-200 lens

Which is better? I know the nikon doesn't get that good of review, but don't know much about the sigma. All of these lens look the same to me and its really hard for me to research them as I don't know which I'm looking at.

There are several different sigma 18-200 at different prices on eBay, which would be the best one? I'm wanting to spend about 300-400 and would probably spring 500 for the 18-200MM nikkor if I can find it (I've found 2 on eBay but missed them by a couple of seconds).