This is a great topic and one that deserves thought and practice. Different procedures will work better on some boats than others and conditions will also make a difference.

In many cases counting on a person to try and swim back to the boat is a bad idea (as Stormster mentioned the wind and current will effect boat and swimmer differently) the only thing worse than a person in the water is an exhausted person in the water. Most people will underestimate distance and effort required to swim back to the boat.

I also agree with sail2wind that cutting the dinghy loose is a bad idea. The chances of the COB catching the dinghy are remote. On the other hand circling a COB with a dinghy trailing the boat vastly increases the likelihood of snagging the COB (like a water skier) much safer than a novice trying to maneuver a large unfamiliar and very hard vessel close to a person in the water.

And if conditions are rough I would rather grab a soft dinghy and climb up on it than try to climb on the transom of a large cat moving up and down in large swells. Yes a dinghy can be hard to climb into but if you've conserved energy you may well make it and even if not, you can hang on while someone from the boat pulls you in.

And of course, throw something that floats, keep your eye on the prize, know how to use the radio and gps.