www or non-www for a new site, does it matter long term?

For rankings, no. Google just treats them as two different hostnames, so what matters is that you pick one and stick to it: 301 the other version to it, make your canonicals and internal links use the same one, and use that version in your sitemap. I default to non-www for new sites because it's shorter on print and in ads. The old argument for www was that you couldn't put a CNAME on the bare domain, but most DNS providers handle that now, so it rarely decides anything.