The little gasser will be easier to start. Those little Zenoah's have a really power hungry ignition system and you may want to investigate that situation before deciding. You'll also have the issues with cold weather and battery life affecting the ignition system batteries as well as the rx batteries. The little beast will burn about 1/3 the fuel the Saito 180 will and it's lots cheaper. Don't know exactly what it'd be as I've not played with one but my 50cc gassers burn about 1oz. per minute, 'bout the same as my YS-110 and I'd expect that the 26 would be about half what my 50cc engine uses.

Glow engines are harder to start in cold weather and if it gets really cold you'll probably need some sort of way to pre-heat the thing but a good electric starter and adequate field battery to run it will be necessary.

While some gassers like ZDZ and BME require high octane fuel due to higher compression ratios, most do not benefit from using a higher octane fuel than the manufacturer recommends but it won't hurt anything to run high octane pump gas, whichever grade you decide on just make sure it's fresh and doesn't have any water in it.

Big debates go on about using AvGas in model engines but suffice to say I would not recommend it (being a licensed A&P Mechanic I've been around AvGas a lot) for various reasons including excessive lead content found in even 100LL. Some manufacturers like Desert Aircraft will void your engine warranty if you run AvGas and they can tell when the engine is disassembled.