It would appear that you already know that the Rotax will be far more economical per mile, so the only reasoning you could use for an RV would be.... "I just want one."
40lph will hurt. Most of the RV owners that I know all whinge about the fuel they are guzzling. One has just upgraded his RV6 to a DyonAero Mcr01 Sportster. 150-160 knots on a 100hp 912 Rotax. The 80 HP model achieves 150 knots easily. There's only a could of them in Australia. Not for the feint-hearted with a 2ft wing chord
