Of course, we've moved on since then. We've discovered the joy and safety of neutral buoyancy. We now use medium-pressure air fed directly from our regulator's 1st stage to add buoyancy in a controlled way. And the modern jackets which we have come to know as BCs are, almost without exception, compact, comfortable and available in a range of styles to suit the demands of all types of diver. Myths, however, persist - not least in the club environment, where individuals may have their credibility invested in inaccurate information.
Bigger jackets can contain more air, displace more water and provide more lift.
Bigger jackets also provide more drag, causing you to work harder under water and consume more air from your aqualung cylinder. A diver should be neutrally buoyant at all stages of the dive. If additional buoyancy is needed, there's too much lead on the weightbelt. Putting air in the jacket at the surface should float you comfortably with head well above it. If you are neutrally buoyant at the surface, you will only need to add air to compensate for wetsuit compression as you go deeper.