APTAR is absolutely correct in what he said.

The basic difference is the pitch of the blades. The Ramtech is higher pitch, therefore it will probably have a little less static thrust, but will produce higher velocity(speed)

Kinda like a 3.23:1 rear end gear(Ramtech) compared to a 4.11:1 (Dynamax)

I'm sure others can elaborate on this subject.

Regards, Johnny

BTW Either fan should work very well in your airframe.