Well I have only recently started having experience with UKC. Nothing bad to say about them so far. The shows are nice, the entries cost about the same as AKC shows, registration prices are only a few buck more. They have very nice registration papers, have a code of ethics that is mailed with each registration, which the code of ethics is great! You can also go to the website with questions, problems and get an answer on forum.
No experience personally with canadianKC, I have sold pups out there that are dual registered with them. But I have never dealt directly with them.
I know a lot of breeders that would prefer to use UKC instead of AKC, but AKC has more local shows. I've checked into the UKC and never found anything that I really didn't like. I think they are seeing tremendous growth after AKC and the PAWS issue.
I know with us UKC only has shows in a reasonable driving distance from us 3 times a year, maybe 4. AKC had them everywhere. I do hope UKC expands and has more kennel clubs start that sponsor UKC shows.