I would not base my decision on which type of relay to use by their 'typical' failure mode. I think I saw a statement in one of those wikis where they said electromechanical relays typically fail in the open position. In my experience over the years, quite a few electromechanical relays fail in the closed position due to the contacts fusing together especially where a higher current is switched. Kind of like welding in a way. Same thing that happens to many heaters where the contacts on the bimetallic strip that turns it on/off fuse together & the heater does not shut off.
I think it comes down to cost for most applications. If you can afford the few extra $$s for a SSR, it's probably a better choice for most of the applications we use.
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