I agree 100% with what CGRetired said.
A better question would be what specific engine would be recommended based on brand, model and size.
Horsepower rating are often not quoted accurately so the best advice is from people that actually have flown various engines and have first hand knowledge on performance and reliability.
Right now, my choice for an engine based on your criteria would have to be the OS 55AX.
That said I have not flown every engine in that size, I have only flown the OS 55AX, OS 46AX, ThunderTiger Pro46 along with Magnum 52 4 stroke and OS 70 4 stroke (and a range of 40 size engines) I have heard good things about the Tower Hobbies .75 but I don't know if that carries over to their other sizes.
PS: I also agree with the other posters, I was still typing while they were posting