I'm not sure. AC has some important safety considerations that would make it better even if the efficient was significantly worse.

Switches, fuses and circuit breakers that work with DC are more expensive than AC. When a circuit opens there is a spark, and this spark can in some cases create a conductive plasma. With AC the wave goes to zero and the plasma disappears, while with DC it continues. There are cases where a DC fuse blew but the fuse continued to conduct. Of course this can be engineered around, but generally with larger and more expensive parts.

When someone touches power accidentally, AC is slightly safer. With DC your muscles will grab and never let go. AC gives you a chance to let go. This is a low probability thing, but is a factor.

The guy who wanted us to debate is wrong for one other reason though: I'm approaching the limits of what I know on the subject, while you seem to have a lot more knowledge.