First comment is that the Stihl isn't a true 4 cycle, but has valves like a 4 cycle. They have the torque but are a pita when the carb blips, it's basically time for a new one.
For a four cycle, there are certain advantages- more torque, lower noise and easier starts than two cycle. But thevissue is that the oil needs to stay reservoir-ed in the bottom of the crank case so they have a limited range of motion- you cant, say, invert them.
In 4 stroke there are only two serious choices: Honda and Dolmar. Honda make great engines, period. But their trimmers are heavy, as already mentioned. Great performers...heavy.
Dolmar 4 cycles are excellent machines, not very well known...but once you try one you will be impressed. They are as light and compact as an equivalent two stroke. And the big deal is that Dolmar have a 360 degree use 4 cycle, including the new multi tool that was at GIE. No one else has that. You should check them out.
