Octane is the resistance to "burn early" which causes knocking, so basically you can take "crappy" gas and make it higher octane with ethanol. So its allows cheaper octane gas to be sold at a higher octane rating. (@ 84-85 octane fuel which no one sells of uses, with 10% ethanol added becomes 87 octane).

There are many reasons to run gas without ethanol. But I can't think of any particularly good for an aveo. It was designed to have ethanol gas run through it, the fuel lines and everything will handle it fine, the programming is good to go. Over time, you might see less issues with the cat.. and possibly o2 sensors. But we are talking very limited benefit.

Older cars benefit, custom builds can benefit, etc.

Now the extra 5 cents for your lawn mower and weed wacker will save your equipment over the years from deterioration. Their fuel lines, aluminum carburetors etc, all get eaten by ethanol.