Meathead

I think more importantly with the original question is that it will be used as a vanity in a bathroom...so there is a sink on top or integrated? With a poly, standing water can cloud the finish and the tests you shared are awesome, but i suspect bathroom products will make their way to the surface and shampoos, liquid soaps and toothpaste left on poly will destroy and break it down quickly. (Experienced....) so now having to sand down to the wood and re-stain, i'm putting my money on spar urethane. Four coats. I contemplated 1/4" tempered glass because i'm not giving up on my solid cherry counter. By the way the hardest part of having a wooden vanity top in the bathroom is teaching everyone to wipe off anything they drip on it. Good luck.