What''''s more efficient?
Your questions gets to the essense of tactics. While you can''t do a thing without good boat speed, the really big gains are made by being in the right place at the right time. The goal is to sail in the most lifted and most powerful wind for more time than your competition. The key is to doing that is to read the race course. The conditions will tell you how often to tack.
On shifty days it is important to stay ''in phase''. In other words on shifty days you tack as necessary to stay on the lifted tack. On steady days you can go further towards the laylines. Unless you are sailing a short leg on a dead steady day with no current you should never bang the corners early. Stuart Walker has written whole books on this subject.
It is a good idea to get out to the course early so you can size things up. You should try to determine how steady the wind is, which parts of the course has the most wind, which parts of the course have the most beneficial or least detrimental currents, which parts of the course are likely to be lifted on which tack. By watching (or sailing up the course) you should begin to get a sense of the pattern of what is happening. Before you ever start the race you should decide how you are going to sail up the leg and where you would like to be on each tack. You need to be watching the course for changes and adapt to those changes but in general, barring something big happening, you should sail your game plan but with caution.
You always want to spend as much time as you can on the favored tack but if you expect the winds to shift big time ''go ugly early''(The term comes from a joke about a guy who always tried to pick up the perfect woman but by the end of the evening ended up going home late at night with who ever was left in the bar. Eventually, he took to immediately striking up a conversation with the homeliest woman in the bar, taking her home and still have time for a decent night''s sleep) . In other words you sometimes need to sail out to the new winds through some less than perfect conditions its can often be better to be the first to do that so you get to the new winds first. You want to be to windward of the fleet on a consistent lift and to leeward of the fleet on a consistent header.
All of that said flyers (going off to some magic spot you think that the fleet has not seen) rarely pay off. The odds are against you when you gamble. If you see that you are going off on your own, unless you are absolutely sure that you are right try to stay near your fleet.
Cross the fleet when you can. So if your plan has paid off, try to tack back when you can so you cna cover the fleet by putting yourself between the fleet and the mark.
When you are out there look at where the really knowledgable sailors are on the course and ask yourself. "Why are they going there?" to make sure there is not something that you may have forgotten (like which mark to round).
Look up the course as you are sailing to guage what is happening. Look at other boats in the area where you are and will be sailing and see what they are doing and mentally catalog what you see so that you can also tell if it has changed over time. Remember what you learned up wind and use the same type of thinking down wind.
If you can keep your speed up, keep your air clear, deal with your fellow competitors, have good boat handling and mark roundings, and still do all of the above you should be able to kick butt and take numbers.
Good luck out there.