Pitch is measured in inches, not degrees. And since you provided no performance data (observed wide open throttle rpm and speed) with your current prop we can only tell you that WOT rpm will drop about 400 Rpm. What happens to performance is impossible to tell without data. At the very top of this forum is a sticky titled "Read This First". Read it.
Less diameter means its easier to spin, looks like you have a speed prop and pulling prop. I would imagine the 17 pitch is for when the boat is empty and light.
Without knowing what kind of boat or motor its impossible to tell you anything more than that.
I tried the second prop and it lowered my WOT rpm by 400-500 rpms but I could stay on plane at alot lower RPM. WOT speed also felt faster even at the lower RPMs. I was looking for a theoretical answer not boat specific but the boat is a 78 bayliner mutiny with a 78 johnson 70 3cyl.
