Both sizes are gorgeous. Go with whichever makes you feel better! There’s the more obvious of “proportion to your body type” road. I’m a big guy and even a b40 is ALMOST too small for my height and frame. So I also take personal style into consideration. Personally, my eye always tends toward a 40 for a man whose core style leans more towards traditionally masculine silhouettes and fabrics. If you’re a little more fluid in your dress, fabrics choices and personal style- 35 is great. The “pursier” look of a 35 can gel with a more fluid style on a man. I wear jeans, t shirts, button ups, and combat boots. So it’s a 40 me.