A 20CC Gas like a DLE20 is about equal to a 1.20 4 stroke. I think now a 4 and 2 in that size are about equal in output.  When you get smaller in 4 and 2 the power output drops in the 4 strokes in comparison to the 2 strokes.  2 Strokes can also turn at least twice as fast as a 4 stroke, but IIRC turn a smaller prop,

I run gas and 4 stroke glow, and the glow is messy, but the gas can get messy too, especially when first running them in, once finely tuned the mess drops to a light wiping.  Right now 10 minutes of running produced a splattering of black oil on the plane with the DLE20. It only has a couple tanks in it though, so a long way to go until its broken in.

Some gas engines weigh quite a bit more than the equivalent glow, the DLE20 is around 28 ounces with the ignition, but you have to also provide a 4 cell Nihm with it, so you need to add that into the equation too.

With the gas, once its broken in and starting on a couple flips, all you need is the gas can and chicken stick, no glow stick or starter needed.  The DLE that I have, once warmed up will start on one flip.  When cold though I use a starter, or I will be flipping for quite some time.