In the context of building PID controllers for very large heater systems (ovens, kilns, etc.) nearly all the designs I encounter use an SSR to switch the load, a choice I don't understand.
The power requirements can top 50A at 250V, where even a reasonable-quality SSR would be expected to dissipate something like 40-70W. By comparison a mechanical relay for the same capacity and quality is dramatically more efficient, doesn't come with inconvenient cooling requirements, and is 5-10x cheaper even on a bad day. Plus, EMRs generally fail open, which is a plus for heaters.
You could argue that SSRs have the upper hand on longevity and moving parts, but certainly not to a degree that justifies the price differential and special cooling requirements.
So... what's the benefit for SSRs here that I'm missing? Why are they preferred in so many designs?