OK, I kind of anticipated the answers I would get. The reason I asked the question of "why" is one coach many years ago weaned me off of quite soft rubbers in general, suggesting that it was a bit of a crutch that would actually hinder development over the long term. He gave me this advice based on his own personal experience, which was based on advice he had gotten in China and Korea. Right now I am using MX-P both sides and might use T05 if it wasn't double the price. (I'm not saying everybody should use those rubbers on BH, mind you, far from it, just mentioning my own preferences).
I think that as someone else said, this is largely a matter of taste, although it would certainly have an effect on how you might hit the ball.
However, the idea that softer rubber would somehow enhance "development" of a stroke --- I don't think I buy into that idea, at least not as something that should be accepted without question. (Or in other words, I strongly question that premise).
The other thing of course, is the OP's original statement that he is happy with what he is using now. So...????????