I'm new to MikroTik equipment, so perhaps this worry doesn't apply, but I've had far more wall warts die on me than internal PSUs. I know enough about power supplies to guess that there are two causes for this:
- wall warts are super-competitive on price, leading the manufacturers to cut corners that I would expect your Latvian EEs to avoid
- they have to fit in a space that doesn't permit proper spacing out of heat-generating components; putting power semiconductors right next to electrolytic capacitors is a great way to produce something that'll die in 1-5 years
I'll gladly pay extra for a half-width 1U metal case over a small plastic case so you can fit in an IEC 320 inlet and an internal power supply. I don't care which connector type you use — clover leaf (C6), figure 8 (C8), good old C14 — but given two switches with the same specs that meet my criteria, the one with an IEC inlet is the one I'll buy, within a reasonable cost margin.
It'd be different if wall warts lasted forever and there was broad compatibility among devices using them so we could get to a world where we wouldn't have all these wall warts to keep throwing away, but we haven't gotten to any kind of a universal DC standard yet, so I'll put more trust in a designed-in PSU than whatever's cheapest from China at the moment.