Quebec City wins hands down. My parents lived in Montreal for several years and I visited often. It's a lively city with much to see and do but Quebec City has more romance and charm and flavour of Europe. The people of QC are friendly with lots of joie de vive.

About hotels in QC, I would not stay in the Chateau Frontenac unless there was a great sale on - the rooms, even those with a view, are very ordinary. Visit to have a drink on the terrace overlooking the river but stay at one of the city's many small hotels.

Consider Ottawa too. So many attractions plus natural and architectural beauty: http://www.canajun.com/ottawa/tourism/

I have stayed at Les Suites in Ottawa many times - huge apartment suites and a terrific location: http://www.les-suites.com/

Some photos of a recent trip to Quebec City - the only one of public interest is the shot of the Frontenac from the river valley: http://www.ualberta.ca/~pletendr/cstm-2000/

As others have noted, it's possible to visit all 3 in one trip. Be sure to check what's on in each city for the time you plan to travel (either to join in the fun or to avoid the crowds), as all have many special events.

Cheers, Pat