really it depends on what you are looking for your phone to do. if you are just looking for a decent phone with a web browser blah blah blah. i think you’ll be fine either way you go. by windows mobile OS, i’m referrring to the OS on the phone. not your computer’s OS. if you use windows, either OS will sync fine. i don’t have much experience with the windows PPC’s, but everyone i’ve talked to who uses it complains about the reliability of it. IIRC, Dr. Dos uses a PPC, and from what he’s said, he likes it. he’s about the only one i’ve heard of that is happy with it.
EDIT: the palm OS is very reliable.