How does the volute improve sustain? I'm not saying it doesn't, I just don't see how could it affect the sustain to a degree that you could notice it. I think people sometimes overanalyze stuff like this that make very little, if any, difference in practice at all. Like the other day when some guy was telling me that having no inlays "improves the tone". Perhaps it's just me that can't hear the difference when it comes to things like that.
Anyways, back to the topic. I've built two necks so far, one with and one without a volute and like Setch, I found it easier to built the one with a volute. From now on, every neck I build is going to have a volute. Not because it's easier to build but because of the stability and looks. If it gets in the way when playing, it has probably been put in the wrong place.