Clandestino,
I beg to differ. The ATR has a critical engine and it is the No1. It is mathematical, not about what you feel, and there is a notable difference which one fails, but you will feel this difference close to VMCA mostly. If you have the opportunity to practice in a simulator that can record and later playback your flight (like ATC in Toulouse), you will see that the displacement of the rudder is higher when the No1 engine fails than with the No2.
Anything away from VMCA will leave you with litlle or no noticeable difference. Flying at VMCA with the critical engine failed leaves you with very little to play with. This is one of the reasons that made the rudder bigger on the ATR 42-500 (they took the -72 design) to cope with extra torque and allow you a lower VMCA.
As to getting back to basics, the P factor is much more significant on the ATR than you would have on the Aztec a you mentioned.
The power levers difference in size was mentioned rightly by Smiert Sponiom (I think it's the poster's ID) on another thread. It has to do with a design cock up involving Go around buttons on both sides of each lever. Nothing to do with critical engine identification, but it makes for a good reason nowadays when people ask.
You could ask another one about the rudder cam, very few people know WHY it is here, but most people know roughly WHAT it does, and that you have to center it before take off. (bear in mind rudder cam and rudder trim are two different pieces of equipment)