Peeking into the rock

I am a grownup and I do not use comma splices in the narrative passages. However, sometimes in dialog the comma splice seems to express the speaker's articulation better than "correct" punctuation. But I'm worried because I don't know what's being expressed there. For example:

"Leave them alone, they're not hurting anything."
"Leave them alone. They're not hurting anything."

or:

"He just came in here Saturday, he looked like a hobo."
"He just came in here Saturday. He looked like a hobo."

or:

"I'm not saying anything, I'm not like that."
"I'm not saying anything. I'm not like that."

or:

"They wouldn't give you the time of day, you had to get your own watch."
"They wouldn't give you the time of day. You had to get your own watch."

(sentences constructed at random) Is there the same difference between the comma-splice and short-sentence versions in each case? If so, what is it? If not, what are the different differences? I can hear differences in my mind, but what are they telling me about the speakers? What do these things mean?

On another front, I have a big vermillion squash in the microwave and I'm going to make a rich, rich soup. With sage.

And Emma's feeling better so she went away.