Cons:
Small planes are often turboprops and they are generally noisier than jets.
Seats on turboprops are often not as comfortable as those on jets (in terms of padding, pitch or width).
Small planes often don't have an oven.

Pro or Con, depending on how you look at it:
Seats on small planes don't always recline.
Limited overhead locker space.

Pros:
Quicker to get on/off.