For some reason, I don't find Iris particularly pretty. However, I do think Clover is cute. As corny as it is, I like it's connection to luck. Clover flowers are also more unique than irises.
Iris. Clover is far too whimsical for me and I can't take it nearly as serious as I can with Iris. Iris seems more "name-like" whereas Clover is more of a name more suitable for either a character, a stage name or for a pet.