I don't know about other English-speaking countries, but it feels to me like
Emil has never become "naturalized" as a truly "American" name in the USA. I would expect that any American man I met named
Emil had parents who were recent immigrants from some European country.
Cecil, on the other hand, seems like it has a rather "snooty upper class British" stereotype for Americans, similar to those than
Nigel,
Percy, and
Cedric have.
Cecil itself was regularly used as a woman's first name in the USA in the late 19th and early 20th century. If you look at the USA popularity figures, you can tell it was really being used for girls instead of this just being an instance of wrong sex codes in the SSA data because the peak for girls comes five years before the peak for boys. One of the earliest women members of the U.S. House of Representatives was
Cecil M. Harden of
Indiana:
https://en.wikipedia.org/wiki/Cecil_M._Harden
Because of my knowledge of the above, my emotional reaction to
Cecil is that it does sound more "feminine" than
Emil.