While writing and speaking are two different skill sets, they have much in common, and there are many people highly skilled in both. For instance, Garrison Keillor is both an excellent writer and an excellent speaker. An orator is someone skilled in writing. An adjective for such a person might be "eloquent." Perhaps there is such a word in another language. But I have not been able to think of a good word that encompasses both--a noun for someone who is good with words in whatever form they might come. The definition would be something like, "One who is eloquent." "Communicator" seems too broad, somehow.
The word rhetorician applies specifically to both writer and speaker:
2 : an eloquent or grandiloquent writer or speaker