Let me make this real simple.
A boat tends to rotate in the opposite direction from prop rotation...Therefore a single engine RH drive boat tends to lean left and a single engine LH drive boat tends to lean right.... simple physics. In twin engine boats one drive tends to counter act the other and lateral balance is improved..... whether spinning in or spinning out......... simple physics.
In a twin engine application, if one propeller is deeper in the water than another...while turning or as a result of simple lateral oscillation induced by an uneven water surface (waves)...the deeper propeller transfers more torque than the shallower prop. So if you are spinning "Out" (RH on Starboard/LH on Port) the deeper propeller will tend to drive the shallower (opposite) prop back down into the water.....levelizing the craft. If you are spinning "In" the deeper propeller will tend to lift the shallower propeller further out of the water.....increasing the outward roll of the hull....... simple physics. These forces do not change with steps, 6 blade props, bottom tweaks or any other bandaids.
Now....... As I said many of the current performance boat builders have not built sufficient bow lift into there hulls, added too much constant section or have balanced them too far forward for a given application. In some cases this is due to the builder having years of reverse rotation and compensating accordingly. Spinning out will increase stern lift in some of these hulls...... spinning in will increase bow lift ( actually reduce stern lift) in some of them as well. To me that means that there is something wrong with the boat...... not the prop rotation.
No matter how much speed you think you may be getting from reverse rotation.....the reality is your lateral stability has been forever compromised.....and some of your hull recovery in high speed turns and oscillations has been reduced.
This doesn't mean that hulls set up to spin out never barrel roll and hulls that are set up to spin in always do. It simply means that there is more of a tendency to barrel roll and roll out ward at the wrong time with a backward rotaion than with the traditional right on right/left on left set up.
In the years (decades) that I covered Offshore racing from a helicopter, I got to the point where I could spot propeller rotation from a distance simply by the added oscillations in straightaways and awkward turning machinations of the hulls spinning in. At least one World Champion thanked me for telling him to reverse his rotation from in to out before setting a World record on a particular race course. He lost a mile an hour on top end but reduced his time around the course dramatically.
There are some who will fight this simple fact to their graves and a particular era of 36 Skater that may have been tweaked to run counter rotation ( interesting that MTI's have this "tendency" too.....wonder where they came from? )
But as I said.... The facts is the facts.