I just returned from a trip that included both the Empire Builder and The Canadian. It is tough to compare them.
The Empire Builder and Amtrak are providing a service. They go daily and a number of people ride it regularly. You meet people in the dining car who say things like "I take this to and from (wherever)." or "I don't like to drive/fly so I use the train to visit (family members/friends)"
With "The Canadian" VIA Rail provides a service to some people, but in the sleeping cars you mainly find people who are making the trip just this once or maybe they do it every few years. My wife and I met a lot of people from a lot of places, but not many Canadians and of the Canadians, most were taking an "I've always wanted to do this" trip. Those of us who considered ourselves railfans all said our trips were prompted by Fred Frailey's January 2014 article in Trains Magazine.
So here we were, Minnesotans at "train camp" on The Canadian with people from Australia, England, Northern Ireland, British Columbia, Ontario, Arizona, Texas, Louisiana, and California. We had a great time and nearly free reign in the Park Car for the entire Vancouver to Toronto journey. Those of us who'd traveled Amtrak before were impressed by the amount of public space there was for sleeping car passengers. On Amtrak, my wife and I are generally in our room if it is not meal time. On The Canadian we spent very little time in our rooms (we did two Cabins for 1 [roomettes] instead of a Cabin for 2) during the days.
The Australian in this band of "train campers" had traveled extensively on Amtrak and said, "Amtrak is like the hotel you stay in while traveling on business. It's good, few complaints, if any, and you'll stay there again the next time you're in town for business. The Canadian is like the resort you visit to celebrate an anniversary."