As far as cost goes the 7D (refurb) is available on the CLP for about $1085 + tax IIRC. The 5D2 is not available on the CLP. My first 7D was bought new on the Pro9000 Mark II printer deal (2+ yrs ago?). Liked it so much that when I found out about the CLP I bought a second one. I think the 7D is a great camera for wildlife and birds ( and a lot less expensive than the 1D4
There is a knock on the 5D2 about its autofocus. A lot of people will tell you that it isn't really true and they have no problem. I started with a 50D and its 9 cross AF points. The 5D2 has 9 AF points but only the center is a cross. When I added my first 7D its 19 point (all cross) AF made a big difference to me. If you are shooting landscape I see no problem with the 5D2 autofocus. If you are shooting weddings and events I think the 50D AF would be a help but nothing big. But for birds and wildlife the 7D AF makes a big difference.
Then there is the "crop factor" thing. Folks who don't shoot birds will tell you to just get a longer lens. I was able to eventually get a 500mm f/4L IS which yields a FOV like an 800mm on a FF body. There was no way I could spend for the 800mm. At times my 500 is "shorter" than I need and I add a 1.4x extender getting a 700mm f/5.6 IS with a 1120mm FOV on the 7D. If you add a 1.4x to the 800mm f/5.6 you get an 1120mm f/8
lens that wont autofocus on the 5D2. It may focus on the 1DX if Canon fixes the "problem" with its "no f/8 AF".
For what you shoot I'd go with the 7D. If you change to weddings I'd go with the 5D2. I'm thinking of adding a "Landscape Kit" to my birds and wildlife setup and would buy a 5D2 myself for that.