Looking at a graphic of London from the 2015 election, I now see that the 2 x LPC and 1 x NDP ridings seem to be surrounded by CPC ridings. So I'm more convinced that the pocket of NDP supporters in London who can currently manage to elect a NDP representative - at least occasionally - get a fair shake from FPTP that they might never otherwise get in a multi-member riding. And, looking at Canada-wide results in general, it is clear that "locality" matters and in a densely populated area the political flavour of the population can change dramatically. But having lived in Metro Vancouver for years, I already knew this. Larger multi-member ridings mean shutting some people out too much of the time.
Representation is population-based. It doesn't have to be perfect, but those who want to have angels-on-a-pin discussions may go ahead.