It boils to to this: if gapless playback and long battery life are what's important to you (and you don't mind re-ripping ALL your CDs to achieve gapless), then it's Sony all the way. Otherwise, go Creative! I've had three of their players; all generally reliable, all sound good and all support WMA as well as MP3 (Sony doesn't ... yet).
I have a IPOD Mini 6G, I have a Sony HD5, and I have a Creative Zen Xtra 30G.....the Sony comes first, just before the Creative, and the IPOD lags some way behind.