Actually if the valve is vertical there is no water trapped in it. Especially if you leave it half open for a day before closing it off in that orientation.

All of my ball valves are vertical except for the combo valve used to shut off outlet flow from the heater. All the rest are plumbed vertical to make sure that all water is out of them when I want them dry.

I also am only talking Jandy Neverlube 3-way valves. No sense wasting 2/3 the cost on lower-end/no-name valves for the 3-way ones.

All the rest of the ball valves are Nibco brand valves rated for pool use. Interference fit ball closure with no seals. The only seals for those valves are in the stems. Unless you get a ton of dirt in them to gum them up, they should operate and seal pretty well. On the return side of things I have little concern, it is the suction side that would get all teh gunk trapped in them, if at all. And being vertical it should help them even in that regard compared to ones laying horizontally.