one of the major things that kills electronic circuits happens at switch-on.Can I ask what you mean by ‘more reliable?’
I only plug in my HMS and TT2 when I use it. I worry about power surges in the house.
the sudden inrush of power is not good.
Like a light bulb that goes blink at switch on.
Also some circuits reach a sort of happy equilibrium after a certain time, so if left on, they remain there!
Stand by (if designed correctly ) means all the low power critical sections remain on, and only the power wasting sections or possibly those bits with a known limited lifespan get switched off (Vacuum tubes, hard drives, certain capacitors). So the device remains standing by for action at switch on.