16gb cause for iPods atleast the size matters cause you may have a lot of music, and never know when the next "best" ipod is around the corner
-But its also better for just your general music needs, with perks of having an awesome touchscreen, safari, the list goes on
IF you want a big iPod for yor "collection" of music, then I suggest going with a "Classic" iPod
I started with an 8 gig from Best Buy, then when something went wrong with it and they didn't have any 8 gigs in stock to replace it with, I paid the difference and went up to a 16 gig. Then when something went wrong with that one, they replaced it once and the next time I just said "gimme the money back" and waltzed into an AT&T store and bought an 8 gig iPhone...