It really comes down to space. Is 8gb enough space for your music and apps? I would say, as long as you get the warranty (depending on the person, their life expectancy is anywhere from 5 weeks to...unknown), you would really be ok with either. As for the faster processor, unless you are sitting there constantly switching songs/apps and messing with it, you probably wouldnt notice much of a difference. If you plan to be constantly using it, or if you plan to use some high performance apps, then the faster processor may be a nice thing to have.
Thanks, i chose the 8gb one because its enough for me