Had a listen to them the other day (they're both on demo in store) and they're very good. I've never really been overly keen on the Mini Zeppelin, and find the i-deck 100 a little fuller sounding than the Mini Zep, which has always been a little tinny for my ears.
The i-deck 200 is the real star though. It'll play pretty loud without losing track of what's going on, and sounds good enough for many to use as their main system, if all their music is on their iPod. It has the bass extension that the 100 misses, and while it's not as full sounding as the larger Zeppelin, it's nicely balanced and doesn't sound bass heavy (therefore, less fatiguing), so some may find this has an advantage in smaller rooms. Either the Zeppelin or the i-deck 200 will suit a larger room, and would come down to personal taste a to which you'd prefer. The i-decks don't have AirPlay, but I don't see that being a problem for many people when they hear how good they sound.