I have the Maysis and have not tried the others. But from my experience they are a pretty stiff boot. I'd say all-mountain stiffness. I wouldnt compare boots by using only their numerical rating because every company uses a different scale.
As for The Maysis boa system I really like it. Do I use it a lot? Well, depends what you mean. I of course use it to tighten my boot at the beginning of every day but that's it. If you feel the need to make frequent on-the-fly adjustments then yea it would be great. Sometimes I want to have a more chill day so I loosen the inside boot a bit. Very quick and easy. But for the most part I just set it and forget it. It never loosens up throughout the day.