What I learned as I researched is that it’s quite tough to pick the “best” white T-shirt — there’s just as much of a case for a structured boxy tee as there is for a plain cotton Hanes.

To help you narrow your search, I consulted a panel of stylists, fashion designers, and all-around cool people to find the best long-sleeved T-shirts for men. I also tapped several of my ...