which one of those 2 figs you like the most in taste and sweetness?
I want to plant one of these two in ground ( zone 6b).

second question: which one of these two produce more?

MBVS is the one you want for planting in ground. For zone 6b it isn't even a question.

Imo the KB out shines the MVSB. The MSVB is more productive, but the taste and sweetness goes to KB, at least at my location.

I'm in 7a and faced the same question.  I went with KB because of the great reputation for flavor.  KB is supposed to be moderately cold hardy though not as hard as MvsB.  So it might require extra care the first couple years until it is established.  Mine was planted in the ground this spring.  The question is how productive KB turns out to be.  There are mixed reviews on this but I'm hoping it is more happy and productive in the ground than in a container.

Location location location.   (For my location, MVSB is the choice.  For yours?  I don't know, but I suspect MVSB will do better for you).

Mike   central NY state, zone 5a

my MBVS was rooted over the winter.. so i won't know until 2 yrs from now. but last yr, Kathleen's Black was very disappointing. i'm hoping it will improve this yr. i heard great things about KB, not sure what happened last yr to the figs. KB is putting on good amount of main crop without pinching this yr. the way the vegetative growth is going, i'm looking forward to breba crop next spring. this spring, i did something wrong and killed all the breba crop.