I'm probably going to get myself into all sorts of trouble with this post but, what the heck! I'd venture to suggest that, over distances of around 200 miles or so, a Dash-8 or ATR will probably take about the same time and cost less to operate than a jet of similar payload capability.
About the only advantages that I can see with a turboprop over a jet is :-
- it can operate to runways that are less well prepared and much shorter than a jet would like;
- it's good for short hops, to act as feeders for larger aircraft; and
- it's probably less wasteful to use a turboprop that seats up to say, 30 people, than a jet that might have capacity for 100 or so, but only 30 seats occupied on any given (short) sector.