Tough one, low octane is not good you can curb that, and ad octane. Ethanol is not good but you can curb that with additives too, well hopefully anyway.
your getting faster cut times with lower octane fuel because the burn rate is faster which means your getting better combustion of the fuel/air mixture in the cylinder, higher octane fuel burns slower which wards off pre ignition (ie detonation/knocking) if your engine runs fine on lower octane fuel anything higher is just a waste of money.
if I had a choice i`d buy the 87 but its nowhere to be found remotely close to me so I stick with the regular around here and supplement with race gas I buy for my car.
Which ever one is fresher. I will drive by an old station in a low traffic location and pay extra for fuel from a newer station in a high traffic location.
I just picked up a new product from Lucas that is made to stabilize gas that has ethanol in it. I'll be using it in my Kombi and saws over the winter, where i'll likely keep scrounging here and there whenever the mood strikes. I've been using MMO but feel a little better with something made to kill ethanol's destruction.
With or without. Sounds like I am ordering a steak and cheese sub. I would go with. Never had one whiff of trouble with 10% etoh fuel and I have been running it for years.