Floaters are there to protect our shoulders, collarbone, and upper chest. If you want to stop pucks going over your shoulders then hold your feet longer, or challenge the angle more aggressively; that extra centimetre of height isn't ever going to be the difference maker, and it isn't something you should ever find yourself relying on.
Like I said, as a player I've never noticed which goalies have suspenders on their floaters and which don't. But I do notice when a goalie can't look behind his net because his shoulder floaters come up too high, and it makes it really easy to set up scoring plays. Wrappies, passes to the slot for a one-timer, hell banking it in off a leg that isn't sealed to the post because the tendy lost track of the puck. If you can't follow the puck in a scramble because your helmet keeps banging into your floaters, then you've got an issue that's ripe for exploitation.
Any half-ways skilled player will pick you apart if your ability to track and move with the puck is compromised because you're fighting your gear, so do what you need to make it as comfortable and responsive as possible. If wearing suspenders over your floaters does that for you then full steam ahead.