*THE* best???
Hmmmmm. I'd be hard pressed to say there is any one single "best".
A lot depends on the technique you want to use on it, as well as the type of ink you use; combined with certain papers that will determine the type of results you end up with.
110 lb. card stock is a nice weight for card-making--sturdy. But, if it has an ultra-smooth finish, it probably won't accept colored pencil work all that well because it lacks a certain amount of "tooth". Same for using pastels on it, if it's super smooth.
For watercolor work, I'd go with watercolor paper, Fabriano Mediovalis or Arturo.
For solid stamping, colored pencil work, pastels, and watercolor (light touch, i.e. with a drier brush than normal), I prefer Neenah Classic Crest Cover, 80 lb. weight. I also like it for Copic Alcohol marker coloring, when working with detail images.
I'm hoping to buy some in Neenah Classic Crest in 110 lb. cover, however, to see if that will prevent any bleed-through of Copic to the other side if I want to make a
single-layer white card. If it tests without any bleed through, I just then may have found the perfect card stock--at least, for my needs/preferences and mediums I like using most, at any rate.
The trick is to find card stock(s) on which both the ink and the coloring medium you wish to use perform not only very well, but, very well
together. It's kind of a 3 component gig. *chuckle*
A lot of this boils down to personal preference, and does require experimentation to find. ;)