Confucious say me think prop rotation confusing thing; the way I was led to believe; or the way I understand it is, we have 2 debates going on here over a single problem.
1 - is discussing open propellers and rotation
The open propellers - the reason that they affect manouvreability of the vessel so much in the way that they turn is because of a syndrome known as 'paddle wheel affect' - this is where as the props turn there is a tubulance built up on the tip of the blades which act as a paddle wheel trying to pull the vessel to the same direction as the rotation of the prop. If the prop turned outboard it would try and pull the vessel slightly to the port. So, therefore, on a twin open prop vessel, both props turning outboard would mean that the thrust was going either side of the vessel and no thrust would be upon the single rudder. If both props turn inboard the thrust from the tips of the propeller are forced into the centre line or the keel of the vessel. As the vessel moves forward the thrust is directed mainly in the centreline of the ship giving more mobility to the steerage of the ship.
2 - others discussing enclosed props as in cort nozzles
With cort nozzles you cancel out the paddle wheel affect and create a similar affect of a water jet - where you have no escaping of side thrust off the tips of the prop and it is all directed out into 2 even thrust patterns and you will find that on all 'fixed' court nozzles you will have the rudders set in the middle of the flow path. In theory it doesnt matter which way the props turn inside the cort nozzle cos the thrust is still going in the same direction and you have no paddle wheel affect.
This is just a brief explanation as I understand it. The other thing is the closer the tips of the blades are to the inside of the nozzle the more affective it is and also the actual inner shape of the nozzle affects the performance.
Last but not least I did a grand search of the web to see how many photographs of the Aziz build I could come up with - and to find out which way the props turned and guess what came up TugKenny on a good few occaions - a red Aziz sinking at Whickstead bows to the sky.
In my book these are 2 totally different problems