The Music of Words: Short sentences versus Long sentences
In writing and in speech, a period is what gives pause, be that may, a short pause at the end of a sentence or a longer pause at the end of a paragraph. It is differential to a comma that provides no pause, but a change in tone, similar to a side note or side thought. Like a musical composition, words are the notes while periods and commas are the breaks. Short sentences provide a more definitive statement. Long sentences, of 25+ words, are more complex with a rhythmic pattern directed by commas.
Which is better?
It depends on what you are writing.