I like the Echo and Stihl engines the best. I've gotten great service out of the Homelites and Ryobis as well however. I have a Ryobi 31cc in my big 76" wingspan Tiger Moth biplane, and it is a "match made in heaven!" I have a souped up Homelite 30cc in my 72" Giles 202. It flies it just great. These engines aren't quite as light as purpose built R/C engines, but they are of higher quality than the Chinese imports, and what's the use of having a really light engine, and then having to add lead ballast to balance the airplane? All my planes balanced without lead anywhere, even with the somewhat heavier conversion engines in them.
AV8TOR