Colludium , I think that Chrome having better overall performance (despite stuttering) is common for the most cases.
As for your old sony machine and its poor performance, while I understand that older and weaker hardware can't simply perform as well as newer and more powerful machines do, I believe that the phenomenon that we describe can't be related just to plain horsepower. If indeed it is, then this is truly disastrous for HTML5/browser based games, because my system (for example), while quite old and underpowered by today's standards, can still run Crisis 3 at high settings, so our examples should look like a joke in comparison, considering that the CPU and GPU usage is pretty low while I test them. Also, this inconsistency in performance between browsers implies that the issue has to do with the software side of things.
As for the recycling, I am positive that it helps to gain calculation power out of C2, but at least in our case the difference shouldn't be noticeable, there just ain't enough stuff happening to strain the machine.
TiAm , I feel the same way, like I am not alone on this, but on the other hand, what can we do? This looks like it is inherently depended on the way browsers work. Let us hope that this is something reasonably easy to fix/improve and that our collective experiences written here and elsewhere will help the developers to do just that!