I have a showtime 50 with a saito 91. Currently running a 15x4 prop. Would something else be better? According to the saito manual, props for aerobatics are in the pitch range of 9-10. This seems a bit fast to me. I thought it was all about thrust. Could someone please clear this up for me.

That 15x4 should do fine. I run an APC 15x4 wide blade on my OS .91 four cycle. That long diameter and low pitch give great static thrust and it should be a good combo with that plane for 3D and vertical climbs. If you want a little more speed than the 15x4 gives you, try maybe a 14x6.

In my experience, I've found that the manufacturer's prop recomendations are a fair starting point, but rarely right on.