@johnnyz - my own opinion is that a bit bigger size is better for comfort, but worse for allowing leaks to escape out to your pants. Ones that fit more snugly hold everything in place better.

Keep in mind, if you’re like most folks, you’ll have a pad in there as well, so you need to allow a little room for that. I’m 5’9”, 175 lbs, and I wore Depends size L pull-ups with a heavy Kroger pad/guard, and that worked well for me. By the time I was ready to move to medium-weight pads/guards, I no longer needed the pull-ups - my leaking was such that I could wear the pads/guards in my boxer briefs with confidence.

I currently wear size L boxer briefs with a Depends shield in the mornings and a medium-weight Tena pad/guard for the rest of the day. I did buy some size M boxer briefs, and I do wear them, but they’re really, really tight. They’re fine in groin, very snug, but the waistband is a killer, as well as the leg openings.