Horse power is basically torque times speed, so it is possible for two engines to have the same hosepower, but have vastly diferent torque. Basically you can trade RPM for torque. of course the optimum prop for each of those engines will be different, so what you will want to know is how much will it pull and what speed will the plane have, all other comparisons are going to be a bit murky

I have limited experience, but so far i prefer 2 strokes. They do the job just fine, cost less, and for me thay have been more reliable. Your mileage may vary.

A few months ago i replaced a saito 72 with 13x6 in favor of an Irvine 53 with 12.25X3.75 because i was having trouble with flame outs and excessive vibration from the 4 stroke. Some of the issues with that engine were later resolved by using the corect plug, but i still haven't put the saito back on because the Irvine has been doing the job. I didn't take any measurements of static thrust for the saito, but in the air the two engines feel about equivalent (iMO)

Basically what ever works for you is the right one.