Use of non tacky rubber with hard sponge?

I think it depends on your stroke...
With a loop I think the softer sponge the easier to generate spin as the ball digs into the sponge easier but it is generally slower

I play with mxp which is a hard tensor.
I use it because
1. I find it hard tensors more stable in blocking and the short game as I feel soft tensors have too much catapult
2. I primarily play with a drive stroke, I find that I often bottom out the really soft sponged tensors

I think you have to think about what are the strokes you want to play. My practice partner uses soft tensors on both side because his game is based on a super spinny opening loop and he hits everything after that. While I am a third ball attacker who tries to control the short game and drive to finish the point as soon as I can so I use a harder tensor