What's available at the pumps is either "E-10" or E-85; E-90 is not approved for motor vehicle use. They haven't approved E-15 either; go figure. "E-10" is the gasohol that is 10% alcohol, and E-85 is 85% alcohol.
I run whatever is cheapest, generally speaking, it's gasohol or "E-10" in my area. It works; I think the gasohol is a little better in keeping the fuel system clean and free of moisture. Alcohol absorbs water and carries it thru the system to be burned in the combustion process. I've had mechanics tell me that large amounts of water would "gel" in E-85, but I haven't talked to any that have actually seen it. From my limited understanding of chemistry, I doubt it. I've never seen any alcohol/water combination "gel". As for worrying about the plastic gas tanks, most vehicles have them and run gasohol with zero problems; not a problem. My truck is E-85 compatible, and the mileage sucks even worse when running it- I'm lucky to get 13-14 mpg. To really reap the benefits of E-85, the compression ratio needs to be bumped to around 12 to 1, maybe more. Since it carries less energy, it may work for towing on hot days with the possibility of less heat energy for the radiator to throw off. CART and Indie cars run alcohol fuel for that reason- they can run a smaller radiator and reduce the frontal area which equals higher speeds.