I don't think this is an easy decision.
Rivera will be a more popular choice. He also fits the mold of the type that has been successful lately.....Payton, Mangini, Mora Jr. (well, in year one), Nolan, Lewis, etc. Young, hungry, relates well to the players.
Sherman is a more "proven" commodity. Not a sexy hire, but maybe the safest. Not a lot of "yee-has", but not a lot of "oh nos" either.
Chow will have a LOT of doubters. Even within the team. Yes, Wilson and Leinart will help a lot. But, it will take more than their words to get their full confidence. Still think he's a boom or bust choice. I don't see them stringing a bunch of mediocre seasons together with him at the helm. It'll either be horrendous or stupendous IMO. Hiring Chow will take guts, because the slings and barbs will come.