Which is best to visit, Toronto or Montreal?

That really depends on what you're looking to do.

Well, we like the idea of taking in a baseball game, traveling to
Niagara, visiting a city but also having a "quaint" day-trip
experience.  We enjoy music and the arts, and also enjoy just
absorbing the atmosphere of a place we've never been.  Historical
sites, walking tours.

I'd suggest Toronto then. While Montreal might have slightly deeper
history and "atmosphere", Toronto has a baseball team (Montreal no
longer does), is much much closer to Niagara, and has many interesting
tours to do.

As well, it is close to Stratford, home of the World Famous
Shakespearean festival.

websearcher

Hmm, I'll side with Montreal. You can always take a day trip to
Toronto and take in that ballgame, but Montreal's atmosphere and
history tops Toronto's. As a bonus, another day trip will take you to
Quebec City, the oldest city in North America. "Old Quebec" (the only
wall city in North America) was named by UNESCO as a World Heritage
Treasure.

Quebec City
http://www.ville.quebec.qc.ca/en/exploration/index.shtml

Cheers,
hummer

I'll split the difference and suggest both!

Montréal and Toronto aren't terribly far from each other.

"Getting Here"
Tourism Toronto
http://www.torontotourism.com/Visitor/TOEssentials/GettingHere.htm

If you have the time and the means, you could spend a few days in each city.