Should I keep my 3G or 4G iPod

I just got another 20gb iPod through the Apple Cram and Jam deal. Already, I had a 15gb iPod. I dont need both of them, so I'm trying to decide which one to sell and to keep. Battery life and the extra 5 gb arent that big of a deal for me, but do the extra "secret" functions of the 4G iPod make it worth keeping, aside from the other two things?

thanks

thanks for the advice, its exactly what i wanted to hear! I was leaning towards keeping the 4G, but needed an extra push.

if i were to sell it on a college campus, what do you think a fair price would be for the iPod (in box with all original accessories and its two months old) plus a marware sportsuit basic case, and a usb 2.0 cable. I think the retail for all of that stuff now would be around $290.