I've read a lot of comments by people who would rather have a Halifax team than one from Quebec City.
While I desperately want a 10-team league and would be happy with a Halifax team, Quebec City would make a much better choice for an obvious, simple reason:
A potential awesome rivalry with Montreal!
If Halifax joined the league, who would THEIR "big rivalry" be with...? They wouldn't have one.
Distance plays a big factor... I don't know too many people from other CFL cities who'd make the trek out to Halifax for games, and vice-versa...
Quebec City is the better choice.
No word on a CFL-calibre stadium being built there though, so unfortunately it's probably a pipe dream at this moment.