I will go against the grain here.
I run a 21SE.
Two engines ago I had a Yamaha 150HP 2 stroke on this boat.
The first repower was a new Yamaha 200HP 2 stroke.
3000+ hours on that motor and sold it still running.
The second was also a new Yamaha 200HP 2 stroke.
Cons
I burn more fuel with the 200.
Pros
I only get a few miles mph more at WOT with the 200HP.
I run a bigger prop.
I jump up on plane loaded.
I cruise at a slightly lower RPM at the same speed as I did with the 150.
I have plenty of power if caught in a bad storm with the boat loaded for bear.
It is no longer a dog when loaded with a full tank of gas, 200lb of ice and everthing else. HA
Even with the price of fuel today I would never consider anything less than 200HP
If you are looking for speed, while the 175 will have more power it sure is not going to be much more.
You need to take a test ride.