I'm a firm believer in symmetry in designs. Don’t make 2 things that perform the same function different unless there is a significant advantage in doing so.
I’d put the same engine front and back. Make everything else that can be exactly the same. Mount, baffling, etc. would have to be unique, but everything else I’d make the same…
Less issues with spare parts, learning curve…
A Renesis 13B can give you almost 240HP at 8200 RPM. With a 2.85/1 reduction drive, thats 2877 RPM at the prop. The RD-1C from Rotary Aviation is rated at 300HP, so you could add a little boost and not break the redrive! I don't think the 20B would be required for most people!
Just my opinion…