The question is, do we hold the air in our lungs for as long as possible after putting our face back in the water, then exhaling with a quick burst prior to capturing the next breath?
First, I want to dispel one myth about breathing during intense exercise. In no sport does an athlete ever take a complete inhalation or expiration. The breaths during intense exercise are relatively quick and shallow, meaning that a little O2 comes in and a little CO2 goes out with each breath. It is an air exchange, not a deep breath.
The most detrimental part of breathing in swimming is likely not the associated increase in frontal drag, though that can be significant, depending on how the breath is taken, but rather the slowing of the stroke rate. Particularly in shorter races, a long, ‘star-gazing’ breath that slows the stroke rate can have disastrous consequences for both speed and inertia.