We have consulted with a number of engine builders on this who agree E10 is less likely to cause issues. Wright Racing Engines kindly provide the below insight:

“Rotax Max engines are low compression and as such derive no benefit from high octane or E5 based fuels. Countless dyno testing has shown that it is far more important to choose a well known brand from your local busy fuel station and ensure you stick with them. Other engines may benefit from E5 based fuels, however in Rotax classes the 10% ethanol for E10, which is derived from plant based additives, can result in a gain in power.”