When my former airline looked at the Q400, the issues were:
- Big Airplane, takes similar ramp space as a 737-800. Doesn't fit up to a jetway easily.
- High fuel burn compared to an ATR
- Maybe not as good a deal as the RJ's, since the manufacturers were finding financing
The ATR has unbeatable efficiency and IMHO was World's better than an RJ at the mission it was intended for.