I've heard transom saver arguments for 30 years. In the "old" days, before power trim & tilt, they seemed to be a good idea to keep the motor from "bouncing" up and down when trailering. Since power trim & tilt, that doesn't happen anymore.
When my brother bought his Gambler, the people at the dealership chuckled at transom savers and mentioned that the stress and torque on the transom was far greater while jumping on plane and blowing across the water than it would ever be while towing the boat.
I use one to keep the motor straight while towing because I think it looks awful tilted to one side or the other and I believe it doesn't hurt anything to have one on.
All in all, not being a scientist, I don't think they're necessary and just may do what Soonerfan mentioned.
Bill