RE: saito 125 or dle 20
The Pulse 125 is looking for 125 4 stroke, a 120 2 stroke, or a 20CC gasser. In terms of power the 125 4 stroke compaired to the others is the weakest engine.
For economy I'd go with the 20CC gasser with a seperate battery for ignition and an optic kill switch. You can make 2 gallons of gas for under 10 bucks or buy a gallon of 15% glow fuel for 17 bucks. The math says that a 20CC and a 1.20 glow are equal. From what I feel and see the gasser has more get up and go.
All I fly anymore are gassers. Cleaner, no more defueling or running the engine dry. I close the choke and put a stopper in the vent line
But like anything there are trade offs, gassers smell worse in a closed space, and if you use Tygon fuel lines then you need to change them about once a year, they harden.
To solve that I am trying PVC line but the jury is still out on that