That's what I think I read: Armstrong is not necessarily looking for the position that will make the bike the fastest. "It has to be a perfect mix between position and power. If I am five percent slower due to the position, but have 25 percent more power, than that will be better."
Now he may be misquoted. He may be confused, or quoted out of context. Or he's being silly. Perhaps he meant that the 'fastest' position wasn't necessarily the most comfortable and sustainable, which is fine. Perhaps he meant that the most aerodynamic position wasn't necessarily the best overall, for whatever reason. But why the heck say that he'd compromise speed for 'more power'? Wouldn't less power and more speed be even better than the reverse? What use is the extra power if it doesn't increase his speed?