There's no real issue with the Q400, if they are appropriately utilised I.e. not over worked and are well maintained.
Some of the Flybe Q400's are reaching end of lease, back in to the big Q400 pot. One might suggest that's a good opportunity for Arann. The ATR is a no brainier, it'll just slot right in to their fleet. But it's no doubt a tough call for them.