Johnny, the advantage is huge, and IIRC, you cannot use it as a phone (ito putting it to your ear to have a conversation ... it is either handsfree or a kit of some sorts). That thing is a mobile PC, and not a phone/pda combo.
the S710 sure looks nice, and the normal phone keypad definitely useful, however, well for me in any case, it will depend on the processor in the S710 ... I have a TyTN, and its got quite a powerful processor, but with a couple of apps not properly programmed or whatever the case might be, it can become very slow ... my point is that I would say go for the S710 or TyTN, depending on the processors ... I had the opportunity of playing with a P4350, and it is MUCH slower than the TyTN