Karen's recent tarnishing aside...
I like them both -
Karen is sweet and breezy, and
Susan is fun and bright.
I'd rather use
Susan, mainly because I've liked the Susans I've met, much more than the Karens, in real life.
I'd spell it
Suzan because I'm just like that.
Suzan,
Mariel, and
Tom (
Thomas)
- mirfak