Between a mains step down transformer and a SMPS, which would be safer for a bench power supply? I cannot look inside the transformer in either case to judge the insulation quality. But, if the insulation does fail there would be 230VAC at the secondary for the mains transformer. And, maybe 325VDC at the output of the SMPS (is that possible)? I can visually inspect the SMPS PCB to check if there is proper clearance, presence of MOVs, thermistors, fuses etc, but of course cannot see inside the transformer.
So the question is, which is easier to make safer (or screw up)? Which is easier to figure out when new, if failure will be catastrophic in future? Can SMPS transformers fail due to failing mosfets etc? I'm guessing that if a mains transformer works without issues when new (including the problem of interwinding capacitance), I can expect it to work for at least a decade without issues, right? Assuming everything will be fused properly and fan cooled.
It's one thing to get a shock from inadvertently touching bad wiring, and quite another to be exposed while clutching the wires in my hands. So I am concerned somewhat about safety. Of course, an RCD/RCCB should probably be put in, but I don't have that yet.
[PS: I'm planning to put a buck converter and then a linear regulator to drop and adjust the final output voltage, be it the SMPS, or the mains transformer.]