yup ethanol fuel sucks, its crap, wish more places gave you the option to NOT use it!, would save a lot of folks a lot of issues with tons of small motored things!
as for more MPG's
yes it should, as it also hold octane I am TOLD longer, so that and the ethanol making less power(slight amount)
but the gains will be SO small I doubt you would ever notice them on MPG gains
NOW on fuel lasting longer and less fuel related issue's
heck yes you will notice LESS problems from fuel over the life time of the atv