21 or 28 for wide angle?

[jbot]

(Sorry if this is already posted, I tried to search but couldn't find anything).

So I shoot with a 35 mostly. I'm thinking I'd really like to add a wider angle to my arsenal. I shoot street photography almost exclusively.

I'm debating whether to get a 28 or a 21. Here are my thoughts.

21 would be great for very close candid portraits (think Bruce Gilden) and theatrical shots where there is a full scene. But it is SO wide, I'm not sure if it's too wide. The 28 is wider than the 35, will allow me to get nice shots of scenes with context and I find it a bit easier to compose well with a narrower lens. It may be a bit too similar to the 35 though.

Help me make my decision?