Haven't tried sleepers in the US (yet...) although i have in Canada on a two-night journey. And I've spent many nights in a mark 3 sleeper (although not one that was moving at the time - the joys of heritage railway volunteer accommodation). Impressions gained from them were that I think on the whole the Canadian compartment was more comfortable: although I'm not large by any means, I find the beds in the mark 3 pretty narrow, although they're a comfortable length. The mark 3 compartment is pretty cosy for one person, I think with two in there you'd have to devise some kind of roster system so that you weren't both trying to stand in the few square feet of available floor space at a time! The VIA Rail sleeper (Manor class, since you ask
) also scored points for having a khazi in the cabin, although you had to pop the bed back up into the wall to use it. Bit of a surreal experience, sitting on the lav looking out over a vista of snow-covered mountains with the odd elk staring back at you.
Where I would guess the Night Riviera scores many points over VIA Rail is in the ride quality: the track I was travelling over through the Rockies was all either Canadian National or Canadian Pacific, and maintained primarily with goods trains in mind. Not to mention the many steep gradients and sharp curves. So given the dog-rough track I didn't get too much sleep the first night, despite the bed being very comfortable. Much better on the second night, when we were out of the mountains and rattling across the prairies! And VIA Rail's staff seemed oddly schizophrenic, scrupulously polite one moment then verging on rude the next, if you asked them to do anything that involved any effort on their part, so I'm guessing
FGW▸ scores extra points there too!