Been a while since I have posted, but figured I would answer the question. I have 2 Union Lockstitch machines. Shows you what I know - didn't know that Randall ever made a clone of the Campbell. I have mine going pretty slow, and I rarely adjust anything but the tension on the top thread. I stitch holsters, belts and the like. Full speed is wayyyyy too fast for this guy. I could probably get by just fine with a Campbell, but they looked overly complicated and my mentor steered me towards the Union Lockstitch. Being able to get tuning/maintenance advice with a quick phone call was worth it. I can get one in tune in just a few minutes now - and once it is there, it stays that way unless I mess up and try to fix what aint broke.
I have heard from Dan Neagle at Campbell/Randall that the Campbell is much easier to use and only looks more complicated - but since I have never sat behind one, I can't give my impression of it.