Actually - something can be said for both the 4 stroke and 2-stroke engines when flying 3D. When I first started flying 3D all I had was 2 stroke engines - OS .46FX, OS .50SX and a Magnum XLS 52A. Each of these are (as far as I'm concerned) pretty much tops in their class as far as power, performance and maintenance for the 2 stroke lineup. Each give me the low end and top end performance for the kind of flying that I like to do - anything 3D. The prop of my choice is the APC 12.25"x3.75" - it goes on everything I own (in this engine size range).

Recently, after drooling about them for sooooo long, I finally broke down and purchased a Saito .72 4 stroke for one of my new profile designs. I have a little under 2 gal. of fuel ran through it so far and for all practical purposes it isn't even broke in yet. But I will say this about the 4 stroke versus the 2 stroke:
a.) Gotta love that 4 stroke sound!!! It is a more "full scale" sound than the "whine" of the 2 strokes.
b.) The 4 stroke definitely has greater low end torque over the 2 stroke.
c.) The 4 stroke seems to get a little better fuel economy but the YS 20-20 blend that I use is a bit more expensive than the 15% I use in my 2 strokes. This is not a big deal though.
d.) It really peeves some folks off that I have such an expensive engine on a "profile" - and I like that! Yes I know....I'm sick......
e.) The big honkin' engine really looks sweet mounted on the nose of my profile.

The 2 strokes will give you:
a.) A greater high end performance
b.) Lower initial cost and cheaper to replace in case of an accident
c.) Lower weight than 4 strokes (depending on size comparisons)
d.) Less expensive fuel costs (especially if using 10%)

I suppose there are other factors that one can consider but these are a few that come to mind immediately for me. If I had to say which one I like best on my planes I would really honestly have to go with the 2 strokes.....just my personal preference..... Good things can be said for both type engines and I imagine everyone has their own likes and dislikes. I actuallyl like both but for all new purchases - it will most likely be the 2 stroke variety.