Efficiency vs Convenience
The basic physics of keel area, lateral plane, and mass would favor the fin or the fin n bulb shape.
Having said that, the difference in overall performance may be too small to matter for some owners.
Good idea to research PHRF databases. Try to find as many different stats from as many different PHRF regions as you can, as some regions will list very small numbers of models of boat that will make statistical comparisons very inaccurate.
Many years ago I got to race, for a while, side by side with a Schock Santana 23 wing keel sloop. Having a fin keel sloop I could out point him, and it always took him a while to feather the boat back up to his best weather angle after a tack in light air. He told me later that the lack of latteral plane would force him to sag off to leeward and work up some speed to allow the foil shape of the fin to start to really work and once he got some speed up it was not too bad. Given that he had options to sail in shallower waters, it was (like everything else in life) a tradeoff.
There is an ODay 322 in our club with a wing keel. I believe that it's an even less-efficent keel shape with a flat "wing" on the bottom. He sez it sails OK, but is very difficult to get ungrounded.
Your sailing area and priorities have a lot to do with any decision.
:nerd:
Regards,
Loren
ps: if we ever win a small lottery, we would change our 6' draft to 5.5' or a bit less, with a Mars Metal bulb and keel depth reduction. Yeah, it would be $pendy, but it would take some worry out of gunk holing in our river delta region and open up some anchorages.
pps: the guy that wrote that verbiage about the performance of that keel option in the old brochure was "stretching" the truth a bit. Advertising has been known to do that, on occasion. Yup, that's just my opinion, and worth about .02 on a good day.