generally speaking, more octane is better than less octane. car gas doesn't really provide anything good and brings along the undesirable ethanol unless you can find gas that doesn't have it in it. so, aside from being cheaper, i don't see what auto gas would do for you. If you don't mind the cost, keep using 100LL and you'll be ok.
you probably know this but here it is for someone that might not, octane isn't necessarily about power, it's about how smoothly the fuel burns in the cylinder. higher compression engines need higher octane fuel, lower compression engines don't. high compression engines will knock/detonate with lower octane gas where low compression engines will not run any better or worse, generally speaking, with higher octane fuels. besides, the lead in the 100LL is good for your engine, as far as I know, autogas doesn't have lead anymore.