The heat dissipated of the two metals would be identical if their resistances were the same, of course. I'm not even considering the difference in amperage between a 110V and 220V connection, as I'm pretty sure that's not what the parent parent post was in reference to.

I was under the impression that the issue at hand was that using solder for high-load wires was bad because of solder's extremely low melting point. I meant to point out that even though the solder is just holding the wires together, there is still a current running through it, and if the resistivity of the solder is lower than that of the copper, the chances of the solder melting would be quite a bit higher.

I honestly don't know if that's why the parent parent post mentioned that soldering high load wires are bad. I just extrapolated issues that someone might have when using solder on high load wires, and relayed them in my reply.

Yeah i was puzzled by the post too, but solder is no way going to be lower resistance than copper, and if your wiring is heating up to the melting point of solder you have other issues.