tough choice between DA 15mm or 21mm LTD

I like street photograph a lot and scanning this forum, looks like a lot of people are fans of the 21mm.

The pics from Moving_comfort posted earlier are quite compelling argument for the 15mm.

No difference is price, so, that doesn't help choosing as well.

Any suggestions on either?
Akhil

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Latest Work:
City lights http://www.pbase.com/akhil80/beauty_of_night
Street Candids http://www.pbase.com/akhil80/tokyocandids