From BlackTieGuide.com -
"Like the pump, formal oxfords are traditionally made of patent leather but can also be constructed of calfskin which has almost as lustrous a finish when properly polished. Whatever a man’s preference, he should avoid inexpensive patent leather as it will not only look cheap but will crack and peel as well. Conversely, he should ensure sure that his leather formal shoes are highly polished to avoid being mistaken for Li'l Abner."
But the bride and groom's wishes trump all.
"Like the pump, formal oxfords are traditionally made of patent leather but can also be constructed of calfskin which has almost as lustrous a finish when properly polished. Whatever a man’s preference, he should avoid inexpensive patent leather as it will not only look cheap but will crack and peel as well. Conversely, he should ensure sure that his leather formal shoes are highly polished to avoid being mistaken for Li'l Abner."
But the bride and groom's wishes trump all.