Everyone here will tell you that Discourse is better than Vanilla. As far as Discourse hosting vs self-hosting, you get the same software with the same capabilities. The question is whether you want a team of professionals in a dozen time zones managing your site, or do you want it handle that yourself?
I attempt to explain the differences between self-hosting and paid hosting in the FAQ section of my $99 Install offering: $99 Discourse Install – Literate Computing, LLC