My self, the route I have chosen is diesel. The start up cost is a bit more than any of the others but the end result is much cheaper.
You can store diesel forever, it is relatively cheap, a 25k gen at 1800 rpm will last forever with minimal intervention, I can run my tractor my truck and my gen on 1 fuel. I can run a 100 gal tx tank in my truck and store it in the barn with the tractor loader. In a pinch I can steal it.
We have a winner
Diesel is by far the best choice, in terms of cost, storabilty and durability. In addition - in a pinch a diesel will burn other fuels such as kero or blends of diesel, kero, motor oil/hydraulic fluid and even a % of gasoline; If you have heating oil- T off right from your heating oil tank. With the low cost of chinese made yanmar copied generators, there isn't much excuse for using anything but. If all you want is a little 2.5kw set then ok, but 5-10K ? these are readily available in diesel models at a small premium.