More RPM's out of a 2 stroke, more low end power out of a 4 stroke. So higher speed with 2 stroke, more 'get up and go' with 4 stroke. 4 stroke uses less fuel, sounds a little more realistic.

Pulse is not a 3D plane; it's a sport plane that can do some good aerobatics. Personally I like the 2 stroke setup because you can do things fast. If you want to get into 3D in the future, maybe a 4 stroke is the way to go. At least for the 40 size Pulse, people recommend the larger end of the recommended 2 strokes.