les liens du Colibri
"Now we spend far less time (3.5ms vs 14ms in this case) in layout for the same number of elements and the same visual appearance. It’s important to remember that for some contexts you may not be able to choose Flexbox, since it’s less widely supported than floats, but where you can you should at least investigate the layout model’s impact on your performance, and go with the one that minimizes the cost of performing it."

Bref, flexbox c'est plus rapide. tant mieux.
A vérifier dans Firefox bien sur ;) Puisqu'on peut en déduire que toute la branche webkit est donc au top là dessus.
(Permalink)