I'll got shot by naz for this but this is my opinion on them.
The difference is the thickness of the pad. The supreme is much thicker and means you can crank them tight without the straps pushing the tongue or laces area of your shoes into your foot. Thats the good bit.
The bad bit in my experience is they take so long to fine tune to get right that I gave up on them. Many times I thought I had it right and then next time I went bocking I'd notice something else and then spend an hour taking them off, taking the straps off, fine tuning and repeating until I sorted it. Did my head in.
The
Connect plus bindings actually have 2 adjustment buckles. It's not easy to see on the pics but it has one in the normal position and another on the opposite side of the strap, about 2 inches up from where it actually screws into the footplate.
I originally feared this second adjustment created an added point of failure that simply wasnt needed but having used it for several months, its not a problem and holds nice and firm.
I think the Edge bindings also have this but I've not used them.
To answer your question, there isn't a lot of difference. On the supreme you get extra padding but no second adjustment buckle.
You're welcome to come to cardiff and try them both!
I will make a video clearly outlining the different bindings but it wont be in the coming days sorry.