trolling motor prop

Gonna get a backup prop for my motorguide 24v 71 lb. thrust trolling motor. Think I'm gonna go with a 3 blade. Was wondering if you guys had any suggestions as far as if I should go with a standard plastic or a glass filled prop. I fish shallow a lot and quite frequently encounter rocks and other underwater obstacles with the trolling motor. I hear the glass filled is more rigid and therefore hooks up so to speak quicker when you engage it. But I wonder if that also means it will break easier when it contacts something solid. Any thoughts would be appreciated.

It's supposed to be tougher than standard prop but if is going to be spare I'd just get cheapest. Have used both and really couldn't tell the difference.

Thanks. The glass prop is only a few bucks more so I think I will probably go with it.