N900 is not that good for navigation. I would go for 808 if you're not into linux too much or if you don't do heavy browsing.

N900 is the workhorse of the three, the most close thing to computer replacement in your pocket. If I have the N900 with me I feel I can tackle whatever job I might need to do on the spot. I cannot say that for the other two. However, my primary phone is the N9, which is a charm for one handed quick and intuitive use.

(Hmm, maybe I wasn't the right person to answer this after all...)