Your question brings another question. How well are you doing managing your current 16g model? It comes down to your behavior. If you believe you have to have every app you have ever downloaded (even though you never use them) or if you want your music library to carry around, you may need more.
Personally, I move apps that I don't use much to a back page. Over a period of time I look through them and if I am no longer using them I delete it. It is a matter of management.