Ah, the heads are tested in isolation and all under the exact same conditions. The big variable is you and your swing. If you just happen to swing a club better, for whatever reason, you will get more out of it. Maybe you get less spin off a Cobra head than a TaylorMade, maybe the sweet spot is lower or higher on the face than the other one, etc. There are a lot of different reasons why you could be getting more out of Cobra than a different brand.

But, at their maximum, every driver head is equal. There was a time, like when Callaway introduced it's Big Bertha that they could say "this driver goes farther" because under equal conditions, it did go farther than any of it's competitors. But, today, every manufacturer is right at the legal limit, and hence are all equal in terms of maximum performance. That doesn't necessarily say what any one individual person is going to get out of them -- and so we're back to the advice, demo, demo, and demo some more.