When i run my tiller with a four blade, i have more bite going backwards at idle and turning ability is dramatically improved. Too much, actually. It becomes very hard to correct if you go to far too fast.
I had a 4-blade on my boat (for 24 hours, then I bent it all to ...)
I not only had great response in reverse, but the forward response, handling, and overall performance would have far outweighed any reverse issues if I would have had any.
And yes, I am buying another 4-blade this winter.