I would think the smaller the tread, the deeper you can keep your foot in it. Like some people like to ride in the "home" position with their foot all the way in the stirrup. (Oxbows are designed for this). I just trail ride and I never keep my foot very deep in the stirrup. I like to feel the ball of my foot on the stirrup tread. I don't like to ride deeper than that because I would not want to get hung up if I could help it.
I believe mine have a 4" tread. I really wouldn't want to go any smaller than regular ropers which I believe are 3". But the 4" are my favorites.
The monels look heavenly to me.