On oxygenated gasoline: generally, the added oxygenates (ethanol?) have less BTUs per gal, thus provide less power than *pure* gasoline.
On the regular vs premium fuel: I have had many vehicles with varying compression ratios/performance engines. I have always tried to use the lowest octane fuel that will not allow pinging on a properly tuned engine in good condition. If 87 octane fuel doesn't allowing pinging, then that's what I use.