Hideho,
The biggest reason to go 4 stroke is the Torque. Swing a bigger, better prop and much less effort. Better fuel economy. 4 strokes have a much more linear throttle, thereby no flat spots or midrange transition problems.
Lower, more stable idle.
Ability to be installed and run inverted in planes without the starting and running problems associated with 2 strokes, (which are many)...like having to start your plane upside down if you have a two stroke installed inverted.
4 strokes expel much less gooo from the exhaust....rarely do I have to clean spooge off my planes that I have 4 strokes in.
4 Strokes sound much better.

Are two strokes more simple?
Yup.
Are 4 strokes worth the extra $$?
Every time.

Ask any 4 stroke owner if he would trade his 4 stroke for two 2 strokes of comparable power....
Answer?
Doubt it, I would'nt.