The three required words is more effective than the four required words assuming that being required really has any weight at all.
Why might 3 words seem more potent than 4 words, and are words ever really required?
Pictures sometimes say more than anything we can muster in the English language. Body language accounts for a majority of our communication. Think about the last time you were in a conversation, your evaluation of what they said had a lot to do with their expressions, posture, movement.
I know of four required words that we see every day in the United States. "In God We Trust" on our currency. I suspect that that without these 4 words the dollar might not be a real dollar.
But there is a 3 letter phrase on our money too, "E Pluribus Unum" appears on all coins currently being manufactured. The motto means "Out of Many, One," and probably refers to the unity of the early States.
And consider the style of three words versus four words.
I am hungry or I want some food
Please don’t go or I’d rather you stay
I hate you or I don’t like you
It’s a simplistic example but you can see that a three word phrase can carry more weight than a four word phrase. Consider that the next time you speak or write.
So the four required words is just an seo contest. It’s barely an interesting topic. The discussion or relevance of words being required is too vague and general, what can be distinguished with much less debate is that 3 words can trump 4.