Having never been to Vancouver, I'd be curious to know why you think it is nicer than SF. I've heard it's colder than Seattle with a lot of druggies and petty street crime.
Aside from that, I think you can attribute a lot of the differences to the simple fact that Vancouver doesn't have any highways going through it or anywhere near the downtown core.
I prefer it to San Fran, but given the 4 degree(C) weather with rain today, I can appreciate someone taking the opposing view.
OTOH, for sheer number of transients it's hard to beat SF.