In Ottawa, if you want to stay in a Starwood property, the Westin is the way to go. It is conveniently connected to the Rideau Centre shopping mall and close to the Parliament Buildings, Byward Market (restaurant/bar/public market area) and just opposite the Rideau Canal. Shop around for best rates (hotel direct, Starwood, Expedia or Click it! Weekends on TravelWeb).
The Sheraton, (which used to be a Hilton which used to be a Four Seasons which used to be an efficiency suites apartment hotel) is starting to be better (only after a severe nosedive in service/amenities), but is still nowhere near the stature of the Westin. If you do stay there, take my advice and eat at the Westin...or anywhere else. Their restaurant is severely understaffed and mal-nourished!
In Calgary, the Sheraton is located close to the airport, and is a typical suburban type hotel. Certainly adequate, but unspectacular nonetheless. The Westin is better.

[This message has been edited by flyme2 (edited 09-14-1999).]