I can not compare 50-85 cc engines as I have only da50 but I have experience with 4 different engines in 100cc class, namely bme110extreme, da100 new version, 3w106 classic and 3w106TOC. For smoothness first comes the bme (runs like an electric) than da and last 3w(I can say 3w really shakes essipecially near idle). For power 3w is consirably superior to both da and bme. 3wTOC>3wclassic>da~bme.