Climbing Rope Hand Feel Characteristics

I’ve climbed on a relatively inexpensive Mammut 9.8mm dynamic rope for years now. It feels extremely soft (not fuzzy) and has a decent amount of give to it when pinched. It bends and knots extremely easily and smoothly, letting you tighten knots closed without much effort  

I’ve felt other similar diameter ropes which are much stiff and slick in comparison. They are much less flexible and do not compress when pinched. As a belayer, these ropes are less comfortable and seem to be harder to hold. The Beal Opera sits on the far spectrum for ropes I’ve experienced with these characteristics  

What characteristics actually account for these differences? Obviously dry treat ropes will be slicker. Is this a generally more desirable trait and does it improve the functionality of the rope? Is there any way to judge the feel of a rope in your hands if buying online? 

They talk about it between 2 and 4 minutes into https://www.youtube.com/watch?v=JnNA4mLqwtQ but say the parameter is not published.