The problem with PCBs in this application is not performance. They work fine (for the most part: I have heard of some exceptions with bad PCBs, those are, well, exceptions
). However, the components on them often have finite lifetimes. Electrolytic caps, for example. When these components fail, the PCB can then become an issue in a couple of ways.
Firstly, they're difficult to work on. In some cases, fiendishly so. The manufacturers themselves
don't work on 'em: if they get a faulty one in on warranty, they don't diagnose it. They rip it out and put a new one in. Your techie will curse and swear working on PCBs.
Secondly, when some components fail, they are carrying quite high loads. All that is separating the conductor leading to the failed component from the next conductor over is...a very small plastic gap. If the voltage difference between adjacent conductors is sufficiently high when a component craps out, it is not uncommon for that nasty electricity to find the next easiest path to ground. You can get arcing and fires and other frying of other components.
So you're right, PCBs work fine. It's when they or the components on them fail that they become an issue.
Don't get me wrong: I bought a Bassman that choc' full of PCB goodness. No problem. It works fine. And as soon as it's out of warranty, the next component that fails will be the trigger to pull those PCBs out and replace them with turret board. Maybe. If I feel sufficiently exercised by it at the time.
It's certainly not a show stopper.
Splat