The bolt-on and quick release axles are the same strength and I never broke a spoke on the hub.
Note that when the hub was quick release, the wheelset was used on a now-sold Sam Hillborne (actually two different now-sold Sam Hillborne frames), a Betty Foy and the Mystery Bike / Protoveloosa. I was changing the rim on the hub from a Chukker to a Cliffhanger to put on the Gus Boots Willsen. The GBW has yet to be fully assembled or ridden.
Truth be told, it was probably more matching the front bolt-on hub than anything else as a reason for the switch (I do not share Grant's fondness for the asymmetrical), plus the cleaner look of the bolt-on hubs vs an actual quick release. I had used a Pitlock on the hub since new and always lived in fear of loosing one or both of the Pitlock keys when I was riding and figured that now was the time to make a change. No chance of a bolt snagging something and accidentally releasing either, not that I am going to be riding through dense brush or anything.
Laing