I've had a 3 since they came out and bought a mini last winter to compare them. I figured I would use both for a while then sell whichever one sat idle the most. The mini is really fun and portable but after the first week I found myself choosing the 3 more often. Purely a matter of fitting my use patterns better - I do a lot of work related stuff on my iPad and prefer the bigger screen for taking notes, reviewing/editing docs, browsing text heavy web sites etc. Even the things that I enjoyed doing on the mini (games and ebooks) I could do just as happily on the 3. The size/weight difference doesn't stop me from taking the 3 pretty much everywhere. If I need to travel really light I rely on my phone instead.
So full size for me. And when the smaller, lighter 5th gen comes out I'll have the best of both worlds.