Good writers are like everyone else - individuals with their own individual set of traits and skills. Some good writers or good auto mechanics or good school teachers are excellent speakers. Some good writers or good auto mechanics or good school teachers are terrible speakers. There's also a difference between speaking in conversation and public speaking.
Words come easily and effortlessly to me - both in writing and in personal conversation. Contrary to what someone else on here has said; I don't spend time editing and constructing my sentences. For the most part.. What I have to say is automatically constructed in my head and just comes out. There are two areas of verbal communication that I'm not good at. One is public speaking. Forget that. I'm not someone who will ever do that. The other is in in-person verbal confrontations when the other person is angry and unreasonable. I really can't hold my own in that setting because I can only deal with lack of reason in on-paper/in-writing debate - not personal debate. I lack the kind of aggression required to hold my own when someone else is hostile and/or unreasonable. Dealing with that particular kind of "verbal challenge" is something other than word skills though. It has to do with being able to be loud and crazy-acting enough to leave others not knowing how to deal with you. lol I think because I'm so "verbal-skills inclined"; I'm "all words; logic; and reason". I don't even know how to be "all emotional and hostile and aggressive and out-of-control"; so I really don't do well when that's how someone else operates. BUT... in one-to-one conversation or in small groups - I'm known as being very natural having conversation of all kinds as long as the conversation is civil and/or friendly.
Note: My weird punctuation here is because my comma key and other keys aren't working in the humidity.