It would depend on team needs. I'd probably lean towards Bailey, but only because a top notch corner is usually difficult to obtain.
With that said, I never saw a clear winner in the Broncos/Redskins trade. Both players were beasts after the trade, and Champ is simply being allowed to stick around for a ring at this point, so his longevity is a little overstated.
The answer is simple and resounding..........................Champ Bailey!!!!
Hated the trade when it happened and must admit that I admire those who say that it was a wash. This fact has surely been missed by some. Champ Bailey will enter the HOF without question while Clinton Portis, will probably have to depend on a senior committee in the distant future to get the nod.