Tom's Networking has a review and comparison of four different PDAs with wireless LAN support (HP H2210 iPAQ, Dell Axim X3 Advanced, ASUS' MyPal A716, PalmOne Tungsten C).
Interestingly, the author comes to the conclusion that "[n]o matter what the construction details are, the Tungsten C clearly outperformed all other products in my test group." Where the Tungsten had a data thruput of 2.7Mbps, the PPC handhelds only achived thruputs from 0.3 to 1.0Mbps.