The topic mentions keel, but the OP mentions also the total hull
shape, beam and volume distribution.
The non-racing boats, both sail and power, are today designed to provide the most internal volume within a given marina slip. The racing
sailboats are entirely shaped by racing rule
The OP is correct that modern racing boats are certainly faster than old racing boats. But for certain, the new non-racing boats, monohull
, are certainly pigs related to yachts that are actually designed to sail rather than pack house-like living volumes into a marina slip.
My boat is a 1983 Olson 40 with a bulb keel (so rail meat not required). I am certainly faster, in any condition, than a modern non-racing boat even up to about 60 feet overall, especially in big seas or light air. Also, the Olson 40 with narrow beam, narrow waterline beam, and very balanced waterlines (almost symmetrical fore and aft) pitches dramatically less than the fat ass / narrow bow pigs of today. It's not even close, it's quite remarkable.
Balanced shapes (fine bow, fine stern) instead of unbalanced shapes (narrow bow, fat stern) certainly move nicer, faster, and more comfortably through the water
. Such boats do exist, even if they are almost none being built new today.
The problems with full keels include 1) much more wetted surface, so slower in any condition and much slower in light air, so one needs to use the engine
much more, 2) Much worse lift
to drag of a long (low aspect ratio) keel compared to a deep (high aspect ratio) keel, and the pointing angle you can achieve is 100% driven by lift
to drag, and 3) Full keels, especially those with a lot of "filet" or fairing between the canoe body of the hull and the keel, results in a lower center of buoyancy, and that leads to less displacement
and more rolling and pitching, hence a LESS COMFORTABLE ride at sea.