Articulate stutterers?

Articulate stutterers? I have noticed that some stutterers are articulate with their speech inspite of having blocks in their speech.They usually know what they want to say exactly but have blocks in their utterances much like a broken record player;on the other hand I have problem both articulating and speaking;meaning I won't know how to put together and explain a particular concept even though I know that concept. Is this because of my social anxiety wherein I have very less practice of actually uttering out my thoughts or is it a by product of stuttering?I just want to be well articulated and not bother much about stuttering. Just a observation I had listening to few stutterers I met in daily life.