Even for cruising there is no question that a folding or feathering prop is a massive increase in speed while sailing. Probably the single best thing you can do to increase the performance of a boat.
Yachting Monthly did a really nice right up of a number of different folding/feathering props, and what they found was pretty surprising.
1) the drag from a fixed prop is roughly the same as HALF the drag from the entire rest of the boat.
2) backing characteristics of the good folding/feathering props was actually better than that for a fixed three bladed prop
3) feathering/folding props has less prop walk than a fixed generally
4) forward thrust from the feathering/folding props was within 5% of a fixed prop.
Based on this study I actually just replaced my fixed with an auto stream, and couldn't be happier. I wanted the flex-o-fold but couldn't find a US distributor. The results have been exacally what I expected. Similar forward speed and control, much better control in revers with less prop walk, and greatly increased speed while sailing.
A reprint of the study http://www.flexofold.com/upload_dir/...onthly_low.pdf