Lets not do the flames folks. They're both good but different systems, so keep the extreme bias out and don't turn it into a playground..
Course, I cannot add anything useful; I have both and other systems. Zodiac is a great great machine in general, but GP32 feels better for controls and has a couple chouce emus since its so easy to develop for (DrMD anyone?
. Zodiac has more polish in a lot respects, and (hoping not to be flamed) GP32 is all over the place for quality since its all homebrew all the time. So if you want a fun homebrew scene on a end of life machine, GP32 is the way to go -- end of life means its got most any emu it'll ever get though they're getting better as long as the homebrewers stick around, but being easy to dev for means theres piles of homebrew (Fenix, C, etc). Zodiac is also nearing end of Tapwave's life likely, but its at least Palm OS and so gets the enormous wealth of available applications and games for it automatically and will thus be developed for for ages to come. So GP32 DrMD is superior to Genesis on Zodiac, but UAE is on Zodiac and not anywhere else. A lot of the emus are the same on both (same codebase, maybe different UI) like CaSTaway. The Zodiac also has some commercial/shareware options which is a *feature* -- the free ones are there too, but you have the option to get supported versions of the emus as well.
Theres also Pocket PC and NGage and Gizmondo; I won't discuss NGage or Gizmondo further than mentioning them
So I can't recommend either Zodiac or GP32 over the other .. they're both nearing end of their supported life, but have very active communities behind them (though I worry the GP32 community may start to dry up a little since the devices seem to be harder to get now .. at least outside of the UK and GBAX. Course, the Zod isn't really for sale anywhere except Tapwave
Hmm, just delete this post
jeff
I carry a Treo 650 smartphone (Palm OS) as my main device; I also carry a Axim X50v most of the time for media playing and gaming and such on the go. I fire up the GP32 once in awhile since its battery based so I needn't worry about charge running out over time, and I play games on a dedicated console very rarely. My Zodiac is not in use right now since I'm a Palm OS dev and thus have a half dozen machines around, and no time to play games so recharging it all the time is too much work. But you can see I'm atypical and not likel yin the same boat as you..