I covered Westminster for years as a journalist (it's very cool sitting in the press box which is a great view of the action) and then for several years with friends' dogs who were entered to help, back in the days when the whole show was held at the Garden. It was always on my bucket list to get a dog to Westminster...I just missed with Checkers and fate never came together for me after her. It's a one-of-a-kind show and if you're into Conformation it's the Broadway of dog shows and I'm very glad the Groups at least are back at the Garden.
Your friend is right, the big kennels who run ad campaigns and target shows for their dogs' visibility do help determine the winner. Shelties infrequently win the Herding Group, although Sprite's breeder and her dog did in 1988, and then of course, Conrad in 2020, the winningest Sheltie of all time who really should have been BIS. I think it depends a great deal on who the judge is, but most years I think there's definitely a frontrunner that's almost a lock going in. It's quite an atmosphere there, unlike regular dog shows, and you need a dog who loves the stage and shines. Win or lose, it's an incredible experience.
So yes, knowing the judge this year I did pick the winner, and I never miss it on TV!