Favorite is such a complex term, too.
Milo isn't the dog I wanted, and neither is Benji. Benji is horribly annoying to be around 95% of the time, and Milo is either a lot of fun or a train wreck, and if he's not a train wreck it's because of a whole lot of training and work and tears that got us nowhere far due to circumstances beyond our control. He's medicated, which makes him safer to be around and in some ways more enjoyable, but less fun and charming and likable. Taking him places is too hard, stressful, and dangerous, and he can't be around my children without restraint on someone's part. If it was my choice, honestly, I'd probably have PTS, but he's legally my parent's and they refuse.
He didn't only change my life, he saved it. I honestly believe I'd be dead without that dog. It's not that I wouldn't be the same dog owner - I wouldn't be the same person. At the height of his improvement before I went to college, I loved him more than my human family and friends. He will probably always be one of my favorite, and hardest, experiences owning a dog. But I don't know that I'd call him my favorite dog. Depends on what you mean by the word favorite. The one I like the most? Hell no. The one who's been the most important in my life? Absolutely.