Without knowing why you want to go from 2 to 3 blade fixed it is going to be pretty hard to help.
2 blade fixed are the most efficient from a "drag while sailing" POV and 3 blade fixed are most efficient from a "power to the water" while motoring POV.
Assuming you are a sailor and not a stinkboater, I'd not recommend going to a 3 blade as it will result in less sailing performance and tend to drive you to motoring more.
Folding and feathering props are best for sailing, with feathering the best of both worlds (and also the most expensive!!!). You get what you pay for. Fixed props have less maintenance issues than folding or feathering.
With that all said, why are you considering changing props?