I've had Both planes and had a 46AX in both.
The Funstar definitely performs better than the Mayhem with that engine. (The Mayhem is a better plane though - (it just needs more power like a Saito 82, YS 63, OS55AX - Jett 61H

)
Go for the Funstar with the 12/4 prop and you won't be dissapointed.
The MoJo is an even better choice though if you are serious about 3d and the 46AX suits them very well.