My bantams have been much more lively and interesting than my standard size (large fowl) birds. My bantam cochins, silkies, booted bantams, and the d'Uccles have been delightful little birds. They chit chat all day, and many of them will fly up to my shoulder and tell me the latest gossip. I enjoy the larger birds in their own way, but the banties have personality galore.
The eggs some of my bantam girls lay are just as large as pullet eggs of the big girls! I get all sorts of colors, too - - we have blue, brown, cream and a nice rosy beige in the fridge right now.
Aggressiveness depends on the breed, just like with standard size (large fowl) birds. Bantam cochins and silkies are the most docile, in my experience.
I had not originally intended to get into bantams, but now I have two coops of them and I would not trade them for the world!