I'm a Glasgow offer-holder for 2013 entry, so it's not like I have a huge amount of knowledge on this, but I was given my offer really quickly after sending off my application (about 24hours) and so in that respect it doesn't seem like I was considered after the Scottish students, and I'm not exactly a student of considerably higher calibre either.
Like someone else said, English students bring money, and they're even offering English students a £1000 bursary for their first year for coming to Glasgow. As suggested, I think it may be more of a reputation thing, everyone who I've told that I'm (hopefully) going to Glasgow has pulled a face and told me not to get stabbed. So I think people overestimate the violence/ roughness of Glasgow.