I think its a matter of tastes, but more info is better than less info, I have done stock, pdaxrom and cacko. Stock, eh, not great, cacko is what stock should be, and pdaxrom is nothing but incredible, havent played with openzaurus yet, but might soon, not sure gotta do more research first.
pdaXrom, big plus, there are alot of people compiling programs for it, I figure its the fastest growing of all the software(rom builds) out there. As for windows managers there are blackbox, fluxbox, matchboc, xfce4, e17, icewm and a few others.
cacko, is what the stock should be, and if you want to run x-apps too there is meanies X/Qt packages(just amazing), a few windows managers for this as well. you can run debian pocketworkstation in dual boot mode or in x/qt.
openzaurus, i hear that they are tring to get thew 2.6 kernel running and all the bugs ironed out, heck maybe they have already done it, again I have to do more research.
oops my bad, OpenBSD, not sure about this, but hear that its more configurable than linux, which is not an easy task(warning: not for beginners, thats why I havent played yet...)
again this is what I observe, opinions may vary, and there is a ton of info out there to make a decision. But dont forget, its the journey that counts, not the destination, discovery is a wonderful thing.