Square and rectangle
I have always felt that a transvestite wore clothes of the opposite sex for sexual/fetish reasons. While a cross-dresser wore the clothes of the opposite sex for "all the other reasons" (stress relief, more comfortable in the clothes, fit better, looked better, etc). So while a transvestite is/can be a cross-dresser, a cross-dresser is not necessarily a transvestite. That doesn't mean that one can't transition into the other.
Just "my" version of the label...