Iris is OK, but I'm not really keen on flower names. Isabel is fine, but I'd use Isobel without hesitation. I don't enjoy Isabella, and I don't like the look of Isabelle.
More of than Isabel fan personally. I don’t have a problem with Iris, but it’s just okay. Isabel feels more sophisticated and regal. I also prefer the look of Isabel, but I also like Isabelle. IsabelIris would be nice.