There have been tons of studies showing that adding additional leucine to whole food meals...and even to whey protein (which liberates and releases leucine into the bloodstream much faster than whole food) results in superior increases in protein synthesis--always.
Why? Because when leucine is taken in free or peptide bonded form, it is released into the bloodstream in bolus fashion, resulting in a large spike in blood leucine concentrations. This spike is mandatory for maximizing protein synthesis...and it cannot be achieved with whole food because it digests too slowly. Whole food, such as meat (regardless of how much you eat at a time), takes many hours to digest, so the aminos (leucine) within it are slowly liberated and released into the bloodstream over several hours. While this provides excellent anti-catabolic benefits, it provides a much smaller increase in protein synthesis. Only by maximizing both protein synthesis and anti-catabolic activity can we accumulate muscle tissue as quickly as possible.
In my opinion, the best way to achieve this is by consuming large quantities of slower digesting (whole food) proteins in combination with supplemental leucine.
This new theory that says "leucine doesn't matter" is ridiculous in my opinion. There is so much research on leucine. We know that leucine is the primary amino responsible for turning on protein synthesis...and we also know that the higher and more prolonged protein synthesis is, the greater our growth "potential" is. Of course, there are many other factors outside of leucine mediated protein synthesis which determine our rate of growth, but to discount leucine's value, given everything we know about it, seems absolutely silly to me.