We've always used the layers of veneer to build up the strength in this, the weakest place on a bass or guitar. Our traditional methods for building the peghead use 17 pieces of wood to reinforce this joint.
If the peghead breaks, it does so in a very predicatable manner. This style is borrowed from violin makers. Every Strad has a new peghead. If the instrument is good enough to be around a long time, the peghead will likely get damaged.
When we decided to make the Epic (our first set-neck instrument), to save some labor, we decided to use a volute instead of the sandwich for strength. Of course like everything we really overbuilt it, including the volute. We've made them a little less pronounced these days.
Until this year, I hadn't see a broken peghead with a volute. And it didn't break at the volute, one of the ears on the side was whacked right off! It was a simple enough repair, but to fix nicely requires the front to be reveneered. With the veneer pack, many breaks are fixed with wood glue, then a drops of good ol' super glue to seal the seam.
The Skylark and Tribute are set neck guitars with our traditional veneer pack. All the other set necks use a volute.
Is a volute cheaper to produce? It depends. When we're making a run of Epic necks, and they are largely the same, then yes. If we're making a one-off Series II with a volute, it might take more time than our traditional way.