I don't do BJJ, but am familiar with it and have done some judo.

In contrast to stand-up striking arts, you have limited possibilities of movement when "hugging" your opponent on the ground, so you need to do have a strategy, do some planning, and have to adapt rapidly to changing conditions. Like "what move can I do in the current position?", "what moves could my opponent pull off form this position?", "what moves could I do if I changed to this other position?", etc. etc.

I do believe that you won't find any better than anecdotal evidence for this subject, tho. Expecially if you'd need to compare between arts.