When bruteforcing

[mastercracker]

True, I forgot to mention workload. You can add some rules to your attack and if the speed increases then it's likely that the workload was not enough to use your GPUs at their full potential (and achieve bigger speed). That said, speed is more or less relevant. If you give more work and it's not targeted, yes your GPUs work more but the attack might finish later than your simpler attack without giving much in terms of cracks.

Edit: My comment is good in general but the suggestion of rules if obviously irrelevant to your bruteforcing.