Well, I will start with my childhood favorite fairy. Bloom, Fairy of the Dragon Flame. She had been my favorite, since I could remember, because she was this special fairy with Red Hair, Cyan Eyes, Dragon Flame Powers, a Nymph Sister, an Amazing Boyfriend, and she had so many good friends.
But as I grew older when watching the show, I had become really mature at a pre-teen age (like a very serious person, I am not kidding), and found some liking to the other fairies.
These are some of the reasons of Why:
I loved how Stella would always have this humor and this fashion I liked.
I love how I could relate to Musa when playing musical instruments.
I love how Tecna is a fairy of technology and how the world can relate to our technology fairy.
I like how Aisha is a defender of feminism, and she is very confident. She has this sporty attitude that brings out everyone's confidence in the Winx Club.
Flora is also a beloved fairy for how her sweet and kindness to plants is deprived. Sometimes... the hatred on Flora is how weak she is, but I love her for who she is.
So, who is my favorite winx? At first, Bloom. As I grew older, it is all of them. So, my answer to the question is that I can't choose between 6 fairies I love. If you want a complete answer, I would just tell you Bloom (from the childhood).