The majority of my gymnasts love floor the best, I have a strong emphasis on floor, as tumbling and handstand etc forms the basis for everything else, so my gymnasts tend to be at a higher level, skills wise on Floor than other apparatus in general.
In general Beam is the least favourite. I believe at least part of this is because they perceive that they are not as good at it, a cartwheel on beam has the same FIG value as a back layout on floor. But it feels to them like they are a lot more advanced doing a back layout on floor than a cartwheel on beam.
Do I have the only daughter who dislikes floor? Dd does not like dance. If she could do floor like the men do she'd probably actually like it! Though she does like it a bit better now that she's out of compulsories. But I still hear, "I don't care about that part, it's stupid filler dance" quite a bit.
My Dd loves vault and bars. She's got a strong upper body so I think that's a lot of it. And she tends to do well on those events which doesn't hurt.
My favorite event in practice is beam. I really like the variety of skills you can work on.
In competition I prefer vault because it is a safe event for me and is over quickly. I have to say that vault has been a love-hate relationship for me. I used to struggle with mental blocks that kept coming back. But once I overcame them vault is an event that I really enjoy because I know I can do it well and it is usually my highest scoring event.