You NEED a large. I medium will be too short in the balls to neck dimension, perpetually smashing your balls. I know this because a buddy made this exact mistake and the M suit was essentially unwearable due to the ball grabbing issue, but otherwise fit OK in almost all other dimensions.
I roll with a size up in my dry suit. Allows for plenty of room for extra layers, and extra beer gut fluctuations, and has limited downside on fit. Might seem huge when you take it out of the box, but when you get your skirt, pfd, shoes on etc, its barely noticeable.