IMHO, 3-blade props on a trainer system is a bad idea. Never mind how much better or worse the performance is, the typical newbie is sure to break that first prop in short order. Now, he's stuck having to buy a new prop AND a new spinner, or cough up some bucks for another 3-blade prop. That's if he can find one in the LHS. I saw this happened to a new guy at our field. He ended up ditching the stock spinner and bought a 10x6 and a new spinner.

Anyway you slice it, it's more hassle than the RC newbie needs to worry about. They should just KISS.

My $0.02.