Open hand vs closed fist.
This is no debate or argument whatsoever, I am just presenting the opinion of my uncle. My uncle is a martial artistist who practiced many styles and currently studying Krav Maga. Recently he visited me and talked about striking and his opinion on how to strike correctly. This is a summary of what he said.
If using a closed fist the target should be 'soft' i.e. belly. If targeting something hard, use the open hand because if you hit the target hard enough you have a chance of injuring yourself. His logic is that as todlers we didn't crawl with our fists, but our open hands.
I agree with him, but I don't think it'd be in my instinct in a fight to use this philosophy.