I thought I would chime in here with my comparison (SL5500 Zaurus, HP 2210 iPaq).
The iPaq really shines in the screen. Both displays are 240x320, but the iPaq is much brighter and the color rendition seems better.
The iPaq is better in battery life.
I really miss the hardware keyboard of the Zaurus when I use the iPaq. The handwriting recognition of the iPaq is better (quicker, but about the same accuracy). On the iPaq, I can write anywhere on the screen.
Software wise, the stuff on the Z wins hands down. I use the Sharp 3.10 rom. The stock calendar on the iPaq sucks beyond belief. It is even worse than the stock Sharp calendar. You CANNOT use the iPaq as an effecient sheduler without spending $50.00 for Pocket Informant or Agenda Fusion (I use Pocket Informant). The multimedia stuff is better on the iPaq. The freeware BetaPlayer (iPaq) is great for videos in divx format. I really wish this was available for the Z. The music player quality is about the same. The Z will allow me to set up parameters for as many WiFi networks as I want. The iPaq will only allow one. This is a show stopper. I use the same Netgear WiFi card for both PDA's. The amount of freeware and the developer support for those programs on the Z is phenomanol! The iPaq does not have the same quality and quantity of freeware. The iPaq has a butt load of pay software, most (in my opinion) high quality. Most of the pay software has an equivalent free version for the Z, but you may have to search a bit to find it. Syncing with M$ Outlook 2000 has been flawless with both the Z and the iPaq. The only flaw with the Z is that the ip address of the M$ machine has to end in .01, with the iPaq, it can be any ip (this is for wireless sync only). The iPaq cannot sync with linux ever. The Z can, but it takes a bit of work to get it set up right.
Overall, if they took the screen from the iPaq and put it on the Z, if somebody ported BetaPlayer to the Sharp 3.10 rom, and if the Z had the battery life of the iPaq, the Z would be as perfect as one could get.
I can supply more detailed info if anyone is interested.
V-Man