What I mean when I say "turning fast isn't the fastest way to turn" is that maintaining your boatspeed is more important than changing course quickly. Putting the helm hard over when you tack can really put the "brakes" on, and you scrub a lot of speed. The result is that you come out of the tack low and slow. Making a wider, smoother turn may help you to maintain your speed, and as a result you will be up to full speed and full point sooner on your new tack. Every boat is different, and some boats can be "thrown" around more than others. You are better off figuring out what works for your boat rather than worrying about turning as fast as your competitors.
Plus, when you are doing a controlled, gracefull tack, you are spending more time heading directly toward your destination as you tack.