Personal opinion but any airline wih 20 +/- planes does not have much spare capacity if a plane or two has to be taken out of service or a flight gets delayed as there is then a chain reaction. By comparison, if you are flying a large, regularly scheduled carrier then there are lots of options re being put on another plane or being rerouted with a partner airline. I don't see that flexibility with a smaller operation and I have experienced both scenarios (i.e. flying a small, charter airline which encountered unexpected delays and flying regularly scheduled, large-scale airlines where planes have had to be taken out of sevice because of maintenance issues). If you have lots of time and no connections at the other end then no problem, however, if you have to make a connection to another airline then I would be somewhat hesitant to book a small carrier, regardless of how good the fare is.