RE: dle20 or a os 120??
I've had both the DLE-20 and OS120AX and can say that power is equal, if not better on the DLE. The OS was a VERY nice engine, and always started on the first or second backflip of the prop. Never had any deadsticks that weren't my fault. But I did get tired of the slime from the glow fuel and also the cost. The DLE is MUCH cheaper to operate and no more slime. That said, it was a little more trouble getting it to start, and tuning is critical. The low speed needle is extremely sensitive and 1/16" turn could make it go from too lean to too rich. However, once you get it set, it runs fantastic. Plus, instead of a 16oz tank, you can use a 6oz and fly for the same amount of time. Plus, gas and oil is available pretty much anywhere, so if you don't have a LHS close by to get your glow fuel from, this could be a benefit. Weight is within 1/2oz for each of them when you factor in muffler and ignition. (I used a one-battery setup so didn't have to worry with an ignition battery. )
So it really boils down to this: Are you comfortable taking the time ti tune a gas engine properly? If so, the DLE is a much better deal because of all the other advantages. If you want to bolt the engine on and fly, the OS120AX is excellent.