I don't know how different an RA is to a Don in Canada, but from my perspective this is how I see it. Don's get free living (free water, electricity, room, cable) but have to pay for their own meal plan. They have to do floor meetings (make sure everyone is doing well, discuss any issues/problems on the floor, make announcements) and activities (pretty much anything, movie night, bowling, whatever).
If you live off campus you'll be paying $460+ a month (Canadian) for rent and utilities, then there is food on top of that. You don't have any responsibilities of first year students (no meetings/activities/etc).
So it really depends on if you want to be a mentor to first year students, how much money you have, and if you would prefer to live with some friends or in a residence with first years.
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"It's hard to get a screw when you're a fan of Doctor Who"