Since your top priority seems to be internet access, my recommendation would be the MobilePro 900C
(which is what I have
). Since it runs Windows CE .NET, it has the latest Internet Explorer, which I've found works fine with most websites and has FTP support like regular IE. It also has excellent hardware support
(as far as HPCs go, anyway
), so you can certainly find a WiFi adapter that will work with it - check the Hardware Compatibility List on here to see which ones are known to work.
A word of advice from someone who just recently entered the HPC world myself: Be prepared to be resourceful and flexible. There isn't a lot of software available for them, although the apps that come preloaded will meet most of your needs anyway. Keep an eye on this site, and a few others, and don't be afraid to ask questions. Despite the lack of support for HPCs, they are still great devices, with more functionality than a standard PDA and more mobility than most laptops. I would also highly recommend paying a visit to www.hpcnec.com, a website dedicated to the MP900C, created by one of the regulars from here.
Welcome to the forums, and let us know if we can be of any further help!