UKC does not allow professional handlers. At all. They encourage breeder/handlers or owner/handlers, but you can't hire a professional. And they're pretty strict about it.
UKC also does not allow for overly groomed dogs. Dogs should be shown in "natural" coat, except those breeds that have a set pattern, such as poodles and terriers. They also don't allow grooming in the ring. You aren't even allowed to carry a comb into the ring.
UKC does not allow the use of bait in the ring. Anyone caught throwing or dropping bait can be excused.
If your dog soils the ring, you get to clean it up. They don't call for clean up, they hand you paper towels and a bottle of cleaner.
UKC frowns on stacking. Dogs should stand naturally, move naturally. In general the UKC requires you to show a natural dog. You can train your dog to walk into a stack, but you aren't supposed to place the feet in any other way; dropping, or picking up a foot and putting it in place are not allowed.
UKC judges are more likely to withhold ribbons for lack of quality. So the quality of the dogs exhibited tends to be quite high.
The UKC point system is totally different. Dogs are required to accumulate 100 points, under at least three different judges, to become a champion. But the number of points awarded is totally different.
UKC also has more titles; Grand Champion, National Grand Champion, for example.
And then there's the Top Ten Invitational. The top ten dogs in each breed may be invited to compete. By process of elimination, it's pared down to ten dogs, who compete for the #1 spot.
My dog, Oli's litter brother won the Invitational in 2004! Thor is a magnificent longhaired Dachshund. Absolutely stunning. Check out his pic.
Thor
That's the kind of quality you can expect at a UKC show.
From the ears back, Oli looks just like him. He just doesn't have that nice head.