It also matters the scene you are watching while comparing. Fast moving scenes or sports are more demanding on bitrate than lets say, a newscast or a soap opera, therefore it will be more noticeable during sporting events. Big events like the Superbowl and the likes are not a good comparison since usually on those the pay providers will allocate more bandwidth for those becasue they know it has a bigger audience. Theoretically the maximun bitrate on an ATSC channel (read OTA) here in NA is 19.53 Mbps I think if the channel only broadcast 1 HD channel , no subchannels , no data casting, no other extra services. Rogers cable could operate on those limits as well specially after they get rid off the analog channels.
Hardcore HD fans will also try looking at the screen at far closer distances , like a few inches , looking for artifacts or lack of detail, (look at the logos and graphics) , but that is not te way the average eye will watch the TV show.
TV Station production, distriubution and broadcast equipment matters as well, usually CBS with ABC very close IMO, has the best picture quality everytime I have compared them during the State of the Union Adresses.
In any case the technology has evolved and encoders and related equipments are better now. I have no means to compare to Rogers or any pay provider now but I do can compare to the few master distribution signals up there on several satellites on C Band and it will also not be fair to compare them to even OTA ATSC. They usually use full TP bandwith (27 Mhz or more) on those C band satellite signals so only 6 Mhz OTA would not be fair to compare.
The larger the TV screen the more artifacts you will see, and I do not know why but usually the Sony's are the worst ones displaying SD content among the big manufacturers. IMO Samsung does way better job displaying SD, but this is all subjective of course.