One thing about reverse rotation is if you hit a fair sized rock, the reverse rotation will tend to spit the rock up and out but a forwards rotation will have the opposite effect. Since the rock can't be driven down into the earth the machine is driven upwards which usually means a lot more force is imparted to the machine then if it were kicking the much smaller and lighter rock up. That difference in force can be enough to break something. Also, while we are talking about forces. when reverse rotation is used, the blade will enter the undisturbed earth gradually but with forward rotation the blade takes a full cut immediately as soon as it touches undisturbed earth. I suspect the reverse rotation would be a lot easier on the machine if being used to break sod.
A reverse rotation tiller will keep shoving the rock to the top of the soil, just in front of the tines, whereas as forward rotation tends to bury the rock again.
As far as digging in quicker, I do believe the reverse rotaion was faster. As soon as my reverse rotation tiller hit the ground, it was at full depth. Always made a heck of a jerking motion on the tractor also. My forward rotation tiller is a lot smoother to operate. But then again, my Massey weighs more than twice what my old Cub Cadet 2160 did, and the Bush Hog tiller is 18 inches wider, and a whole bunch heavier.
As far as tilling quality, I see no difference between my reverse tine Cub, and my forward rotation Bush Hog..........except when it comes fall tilling. The Bush Hog tiller will tear cornstalks, and tomato/melon vines to shreds , whereas the Cub reverse tine tiller would wrap the vines around the shaft, and I wouldn't think of hitting a cornstalk with it.
But then again..........Massey Subcut vs. Cub Cadet lawn and garden tractor with a belt driven tiller.
On large rocks, firmly anchored in the ground..........Either tiller will bounce violently, with the reverse tine bouncing higher.
For breaking sod..........you are correct. The reverse rotaion I found a lot better. Seems like it was better digging from the roots up, as opposed to digging from the top down.