[DavidPlumpton]

What's more likely? That quantum interference appears because many worlds perpetually exist, or because they seem to exist but somehow don't, or because they sometimes briefly come into existence, hang around for a bit and then randomly collapse breaking all sorts of laws (Liouville thereom, CPT invariance etc.)?

Many Worlds is much tidier than all the alternatives.hh

[eli_gottlieb]

Actually, I'd say the "illusion" option is the simplest and tidiest. It is more likely that we interpret a complicated reality from incomplete information than that reality truly is complicated.