Both names are beautiful and classy. But every name nerd knows that
Isabella is a form of
Elisabeth. But that's what's happening when you go by sound alone and don't care about meanings and origin.
Even worse is
Bella and
Beth, way too similar. There are so many other nn for
Elisabeth and they had to choose
Beth (
Elsa,
Elsie,
Ellie,
Lisa,
Lily,
Libby etc).