Thaddeus is ugly ugly ugly. It sounds like a body part, like your thalamus. Thad is gross too, it'th tho thad and lithpy. And Tad just sounds like an asshole of a boy, even more so than Todd.
James is very nice, and it has plenty of nns to lighten it up. Jimmy is youthful and unpretentious but grows up reasonably well; Jim is a handsome, down-to-earth grownup. Jay is kind of sophisticated and smart. Jamie ... well, some people think it's cute, I think it's babyish.
You're entitled to your own opinions. You're not entitled to your own facts. -- Daniel Patrick Moynihan