Canadian ex-patriot here. The switch to dollar coins happened in the 80s, I think, because while bills are cheaper to make coins last so much longer as to make the switch very much worth it from a fiscal standpoint. I know the US could save millions annually with such a switch, though various interests (including the cotton lobby) prevent this from happening.
I remember when I moved to the States for the first time one of my greatest annoyances were the dollar bills. It seemed like I had so much more money in my wallet than I actually did because of those stupid dollar bills.
What people like better is really a matter of preference, but if you like your government to not spend more than is necessary dollar coins are the way to go.