If you compare the firm orders of the ATR 42 to those of the Dash 8-300 - the -100 and -200 series not being direct competitors to the ATR 42 - the respective market shares are 65% vs 35%.
On a typical 300 nm sector in an European environment the direct operating costs of the ATR 42-500 are about 3 % lower than for the Dash 8-300. Nevertheless I admit that a DeHavilland statistic could come to other conclusions. In fact, I think that both aircraft are very cost efficient.
I do agree that passengers influence the decision of an airline what type of aircraft it will operate. But ATR has done a lot to increase passenger comfort, too, and noise reduction was a very important issue. This has been reached essentially by integrating dynamic vibration absorbers which reduce noise transmission from the engins and by the new electronically controlled six blade props. The result is a jetlike comfort for the -500 series.
Max. cruising speed of the ATR 42-500 is 300 knots, range with max. passenger payload is 840 nm, max. payload is about 5,500 kg.
Another advantage is the commonality within the ATR 42/72 family that disposes of common type rating and cross crew qualification. By the way, Samurai777, the ATR 42 has a cold weather certificate to operate at temperatures as low as -52 °C.
I do not say that the Dash 8Q performs worse because I have never been on one. I believe you when you say that you had very smooth flights operated by Dash 8 aircraft, but accept that you could have had them with ATRs, too.
And honestly, Quad Otter, isn't there a strong Canadian bias within your post ? At the end you will have to change your member profile and state that you would like to fly an ATR !!!