While more HP is nice and always welcome, HP alone is not that big a factor in snow blower performance.
To me, the design of the blower itself has a lot more to do with efficient snow removal than how many HP your engine has. The man running the machine has a lot to do with it as well, you can't charge into wet snow at high speed or by using the full width of the machine. You will get clogged up sometimes, its a given. And the size of the engine isn't going to change that as long as you are not using an underpowered machine that is not made for the type of work you are expecting out of it.
I used a 5.5 HP machine for years in Lake County Ohio. Most of the times it clogged was me biting off too much with a pass.
I will say that I upgraded to a 8HP Ariens last year and it was very impressive but it has as much to do with the machine as a whole than just the bigger engine.