If you aren't planning on storing a lot of media, be it music, movies or photos, the 8GB will probably suffice. I had an original 8GB until March. I keep about 50 photos, 2 movies and 1383 songs and I had about 1GB free. I only used 4 screens of apps of the (I believe) allowable 8.
I've since upgraded to the 16GB, but that was only because I wanted white and it's not available in 8GB.
Whichever you choose, you'll love it 🙂