They are very different kinds of prop. The bruntons is self pitching so adjusts pitch to suit speed and conditions and generally results in lower RPM for a given speed. Main benefit is if you do a lot of motorsailing as it loads the engine better when part of the power to move the boat comes from the sails. Very expensive compared with others and the fuel saving will not cover the additional cost.
The Kiwi is the other end of the spectrum. Cheap and simple, but can be unreliable if not regularly cleaned and lubricated. Has a fixed steep pitch in reverse which can cause low speed problems in some applications.
The other alternatives are 3 blade folder such as FlexoFold or feathering such as Featherstream or Max Prop. The two former are similar price and perform well, with the Featherstream perhaps a bit better for motoring.
Drag reduction is much the same on all of them so you should expect a small improvement in speed under sail alone, mainly at lower speeds.
I have had FlexoFold on two boats - a 37 and now a 33. Both two blade and very satisfactory. You will need a 3 blade, but avoid the Volvo version as they are not as well made as others and can suffer from high anode wear (as can the Bruntons).
Hope this helps
