Anecdotal (and risking downvotes), but my opinion: Brazilian Jiujitsu. It's like Chess for the mind while simultaneously getting an incredible workout.
I think for long-term health and overall fitness BJJ is a tough sell for most people.
Wrong BJJ... BJJ is just another form of wrestling, and even then, no head gear is used.
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.