Hi Joe,
You ask good questions. I've built quite a few guns and I have used every manufacturers locks. KLMoors is bang on. L&R locks require a lot more work to get fitted, cleaned up, and tuned than the others. Taylor and others (including me) use L&R locks for some projects because they have the appropriate look for their particular projects. Regardless, the only locks I have used that did not require a great deal of tuning and never had a quality problem are Chambers. All the L&R locks I've used needed a lot of finishing work to get rid of rounded corners, poorly shapes features such as pans, poor fit of parts. L&R is not alone. I had the bolster on a Davis lock turn to dust where I drilled it for my lock bolt because of a huge void in the casting. I had to forge a frizzen spring for a Davis Harpers Ferry lock because the original spring was so weak. I have never had similar problems with Chambers locks. The swivel breech gun I recently posted uses the internal parts from an L&R back action lock. The main spring was so weak that the flint would not move the frizzen 1/8". I had to add 20 degrees of preload to the spring to get it to work right. I typically spend four times the time fitting, tuning, and finishing L&R locks compared to Chambers. Don't get me wrong. They can be made into fine locks but that requires quite a bit of work and knowledge.
dave