Original version: nice! Great vocals! The mix somehow sounds a bit dull though (please note - not dull as in boring!) so you might consider using an eq to brighten it up a bit. Also a compressor might raise the loudness a bit. Having said that, the mix is really nice in that every instrument is very clear. Musically, this is a very nice arrangement with an unsuspected and really cool break at the end. Very, very nice!
Guitar version: brilliant! This one really sparkles, the vocals also seem to come out better. The guitar is great. I have to concur with Kara: it definetely needs more cowbells!
Definetely a song with hit potential.