I don't think it is an either/or. They are not at odds with each other, rather they compliment each other. Collins is helpful with ecclesiastical pronunciation and Wheelock is good for paradigms.
Classical first. Although exposed to vocabulary and styles which might never be used in ecclesiastical Latin, it will provide a feel for the language which theological writers possessed even when they did not express it.
Classical first. Although exposed to vocabulary and styles which might never be used in ecclesiastical Latin, it will provide a feel for the language which theological writers possessed even when they did not express it.