Somewhere else, homebrewers are debating the merits of continuous sparging vs. batch sparging. Among commercial brewers, there's very little debate: continuous sparging rules. Here, I'm going to illustrate how a batch sparging simulation can help you predict your brewhouse efficiencies regardless of the sparging method you actually use. How's that for diplomatic?
As you probably know, brewhouse efficiency decreases as runoff gravity increases. To understand why, it helps to view mashing from a new perspective. Typically, we think of using more grain as a way to increase the gravity of a fixed volume of wort. Instead, you should think of using more grain as a way to increase the volume of a low-gravity wort. When you brew a high-gravity beer, you simply stop lautering before the full volume of wort can be collected. Because sparging dilutes the wort exiting the lauter tun, stopping the runoff early results in a higher-gravity beer. However, it also leaves more sugar behind in the lauter tun. The end result is that the small volume of high-gravity wort has less total sugar than the large volume of low-gravity wort that could have been collected from the same mash. That's why gravity comes at the expense of efficiency.
The method can be refined by optimizing the water-to-grain ratio for each grainbill and generating additional curves for multiple batch sparges, e.g. sparging twice for a total of three runoffs. According to Kai Troester's Batch Sparging Analysis, batch sparging is most efficient when the runoff volumes are equal. I didn't assume that was true when I started, but I ended up with the same result after running my calculations over a wide range of water-to-grain ratios. Here's a graph that shows the peak efficiencies - represented by runoff gravities - over a variety grainbills, water-to-grain ratios and number of sparges.
If you'd like to check out the simulation itself, you can download it here.