Everybody jumping on for the full frame sensor of the 5d and the high megapixels. However the 1d Mark II and the Mark IIN are 8mp, which in my opinion is still fine for portraits, but the camera was designed specifically for the sports or fashion shooter. Someone who needs to take pictures quick, fast, and with high quality. The only camera out there with a buffer close to the 1d models is the Nikon D2hs, but...who wants something with less buffer and only 4 megapixels? One has to wonder.
If you need the speed, go with the 1d models, the portrait quality is also fine. If speed is not an issue, the 5d I feel is a better camera for most. Smaller lighter body, full frame sensor, more megapixels are the surface differences. Buffer although not like the 1d Mark II N, it can still give you some decent burst rates.