2 strokes are cheaper and rev higher since they don't need any valves or a cam and they fire every time they hit TDC. In small engines they also generally use simpler carburetors.

4 strokes are more expensive and require some type of valve setup whether it be cam driven or whatever. A 4 stroke only fires every second time it hits TDC.

It's really hard to compare, because they are two different beasts. If I had to make a generalization about 2 vs 4 stroke peak power numbers, I would be inclined to say that for a similar displacement, a 2 stroke makes roughly 1.5 - 1.75 x the power of a 4 stroke. That being said, I still don't feel that it is an accurate comparison.

The thing to remember is that HP = (Torque x RPM) /5252 5252 is just a conversion factor.

So a two stroke will always have a rated horsepower advantage as long as it can keep making power in the high RPM ranges. Also, Peak HP and torque numbers are highly over rated and mean very little. The shape of the Hp and Torque curves are much more important. The shape you want depends on your application.