There is a danger, if you go too far from the text on screen, that people will lose the thread. It's hard to follow the logic of two arguments simultaneously. It may be easier for the speaker, but not for the audience.

OTOH there is nothing worse than sitting thru a presentation where the speaker simply reads off what's on the screen - especially when they look at the big screen all the time and make little eye contact with the audience. It is really easy to set up a script on the laptop that is separate from the presentation as projected. If you have to look at the script at least your face stays visible, even if the eyeline drops.

My main advice always is that people sell things, presentations don't.

You can't be me, I'm taken