I think these discussions often go around in circles because of the way that we come to define them. Perhaps this will clarify my point. It takes a certain amount of displacement to support the boat and crew. If we have two boats of equal dry load (meaning empty tanks, and lockers etc) displacement, generally the boat with the longer waterline will carry a larger percentage of its weight in full load capacity. Obviously there is a limit to how long an equal weight boat becomes before the boat ceases to be structurally suitable, but withing a reasonable range the longer boat of equal length will offer a gentler motion, a more easily driven hull and so a smaller sail plan making it easier to handle, and will perform better as well.
And By the same token the cost to build and the cost to maintain is larger proportionate to displacement rather than length.
So while we may rightly say that if we compare two boats of equal length, similar hull forms, rigs, and weight distributions and ballast ratios, the heavier one would be more comfortable (up to a point), when we talk about going distance cruising, I think we need to define the displacement that we need to carry of stuff, and then look for the longest boat that can safely do that (which means a lower L/D).