I have an ipod touch 5g, and its 16 GB
Disadvantages-
1) battery life- the battery life of the ipod touch is just 1000 MaH I guess, the battery gets discharged very soon.
2) speed - unlike the iphones, the ipod does not have much speed, it gets slow after 3 months of usage.
3) compatibility- few applications in the app store are not compatible with the ipod touch like whatsapp etc.
4) transfer - you cant transfer anything to a non apple product, it only works apple to apple.
advantages-
1) color- ipod has pretty chrome colors like blue pink grey black etc.
2) HD - the screen is High definition
3) camera- being an ipod its had a great front and rear camera.
its just like a smaller iphone, works great and is everything you need if you dont want a phone.:)