What is the best safety mat?
It's hard to answer this question. Indoor long jump, indoor high jump, pole vault, sport climbing, ...
Each purpose demands own solutions. Each solution has to cope with conflicts of interests.
Boulders sport climbing is a relatively young sport discipline. Enhusiasts are climbing on natural rock boulders with very little protection. Their safety mats are called Crash Pads and offer just basic protection. Such protection is not sufficient for recreational climbing in climbing gyms and in case of official competitions.
The same mat can be flexible for 90 kg climber and very stiff for 20 kg child.
Visible injuries aren't the only problem. Too many jumps on too hard mat can cause stress which will lead to problems with ageing.