Mario has always bashed bricks with his fist even though it looks like his head, but really neither option is a good idea. As illustrated by the Pete Holmes Show, bad things can happen if you try to break apart floating bricks.
Dubbed Realistic Mario, we can see what happens when Mario and Luigi try their hand at breaking apart breaks. I'm digging the video game videos that Pete Holmes is doing and I'd love to see more of these little shorts on old Nintendo games.