In general, changing a prop is obviously simpler and cheaper. Stick with props until you start to run out of pitch (i.e. 36 inches or more) OR you simply can't bring the boat onto plane with high pitch prop.
After about 36 inches of pitch (and again this is a ballpark) there are few , if any, higher pitch choices, so you're forced to do a gear change.
It is generally more efficient to swing a large pitch prop slower (1.5 gear set) than it is to swing a lower pitch prop faster (1.36 gear set).
In your case I'd try a 32 and see if it brings down the RPMs. My guess is you pick up some top end as well. If it becomes a bitch to plane with a 32 you may end up having to do a gear swap.