Those aren't small. I used to fly regularly on a Saab 340 (34 seats) and had some flights on a Twin Otter (18 seats - not that you'd ever have got 18 people into the plane). Islanders are even smaller.

Good side is you don't need to fight over who gets the front row as everyone gets on and off quickly. You don't get people arguing over locker space as the only things that fit in the lockers are handbags and coats. You get to feel that the cabin crew and flight crew are a close knit team - the same team on the Twin Otters).

The down side is that they can be somewhat cramped and noisy. And cold/wet when they park on stand with the doors open.