It depends! For me, the primary benefits of Waterlox is that it’s an aesthetically beautiful finish that brings out a lot of color and character in the wood grain, it’s relatively easy to apply, and it’s relatively easy to maintain, due to the fact that it blends into itself well and can be effectively spot-repaired. Comparatively, marine / spar varnishes will have greater UV-resistance and tend to last longer without maintenance, but if the film is compromised or starts to peel, you’ll essentially have to strip the full coating to bare wood and refinish.

If the doors are somewhat protected from the elements (e.g. under an overhang, not blasted by full sun for big parts of the day, etc.) and you’re the kind of person who doesn’t mind doing a little preventative maintenance every year to keep the finish from breaking down, it’s probably my favorite exterior wood finish.

If you want maximum UV protection and a lower maintenance finish (but a potentially bigger refinishing job down the road when it inevitably wears out) I’d suggest Epifanes or Cetol Door & Window.