Iris is very elegant and nostalgic. I love almost any female name beginning with an "i" and this is no exception.
Isis, on the other hand, is the exception to my love for most female "i" names. I grew up with a cheesey television series starring
Linda (
Lynda?)
Carter as "Wonder Woman." She spun around and said, "Oh Mighty
Isis!" to turn into her super-hero self. Ugh. It was so corny that I can't separate it from the history and value of the name
Isis.
Eris reminds me too much of "heiress" which would be super tacky. It's a shame because
Eris is just the sort of airy, mythological name I usually go for in a big way.