I think the spelling sometimes makes a difference to how the name is said,
Isabelle / Isobel
Genevieve / Jenifer
Margaret / Margaritte
We went with Isabelle - it was the only name DH suggested and we were on the way to the hospital so he caught me off guard a bit.
Not sure I would have gone for Isobel though.
I always think of it as the Spanish spelling as that is where we were living and for the Spanish queen.
Isn't is a version of Elizabeth?