I have the original 5G and I still haven't filled it yet, it depends. Are you selective about music or do you just download or buy every song you hear on the radio. I'm kind of selective so my collection grows at a slow rate. And if you would make practical use of the extra space, it might be worth it to just get the normal iPod, but if not, go ahead and just getthe iPod Mini, you'll be saving $50, you get to choose a color (which sounded like a buying factor in your post), and it's smaller. Based on the facts you've told us, I think I would get an iPod Mini if I were you.
Edit: Sign up to be a part of my iPod user group! 