JET A is the big thing for me. I would NEVER buy a NEW AVGAS powered aeroplane now. You'd be nuts to...If for no other reason as Avgas going out of fashion. Jet has got to be less hassle, and is also cheaper at the moment. But even if it wasn't cheaper, imagine a Twin burning 12 gals per hour.
The oil dropped dramaticly the last days below 90 dollar a barrel...(good news!) My idea is when the AVGAS will not be available anymore in let us say 10 years ? We will have diesel replacements that will work from Lycoming & Continental who will fit in current airframes. Continental is making a diesel engine right now.