Okay, I'm going to give my own answer to my own question.(Had to ask something I could answer, because I don't know anything at all about epoxy and resin and gelcoat.)
Personally, when I am on the helm, I prefer upwind sailing. One reason is that I can "feel" the boat better. Another is that as a child I first learned to sail on the windward leg, learning the correct angle of the shroud telltale and learning how the wind felt on my cheek when I was doing it exactly right. Another reason is that in the monohull world where I grew up, the windward leg was always said to be the leg that "separated the men from the boys." If you got to the windward mark first, you got the respect of the other sailors, even if you were last to the leeward mark. Just thought of a fourth reason, so this has been edited in: Sailing upwind I feel more in control of the boat, whereas downwind I feel more like the boat is in control.

And even as a crew, I prefer the upwind leg to the leeward leg, because I understand the tactics better than I do on the leeward leg, and I like the skills involved in trying to achieve the perfect roll tack and trying to (but rarely succeeding) beat the skipper out onto the wire.

But as a crew, my favorite buoys leg of all is the reach, because it involves the most sail-handling skill and work on the part of the crew. Unfortunately, most buoys racing does not include reaches any more.