I'm more accustomed to driving downtown because that's where I live and work. I'm used to the constant red lights, matching out for parked cars and opening doors, and pedestrians leaping out into the street to jaywalk. I haven't ridden much in the suburbs but when I lived in the 'burbs as a kid (I only rode my bike in the park nearby) I was leery of the wide, busy streets and the cars whipping past. Looking for slower moving sidestreets is trickier in the burbs because they are often crescents and circles and would add kilometres to a commute and I'd still have to cross busy intersections.

My vote for downtown riding.