The planes are so different its almost impossible to compare the two. Without a doubt the building time for the Sig SE will be a lot less not only because the SE is a simpler design, the kit is better. The parts are all laser cut so very little sanding or fitting is required and like sig says you can build it as fast as you can glue it together. My Sig SE for the short time that I had it flew great with an old OS .46SF. Although I have built several GP kits I have not built the Rv-40. I finished the GP Mustang 40 this winter and while it was a easy build it took much more time than the Sig SE. The wood quality will much better in the Sig kit. I have thought about building the RV-40 I think could be a real nice fun scale project esp if it was finihed with a scale color scheme. I think bsp got confused with how you named your engine and thought you were wanting to use a OS .61SF 2-stroke a OS .61 4-stroke should be good power for either plane. You will probably need to buy or make a taller landing gear for the Sig SE if you want to swing a prop with a dia of more than 12"