I will tell you to go out and get some big industrial size rubberband.
Take it and stretch it over the tip so that the tip is completely covered (hence the industrial size) and stretch it down and tie it off on the shaft somehow (it's not that hard)
Then try and shoot with it.
You will soon find out that unless your stroke is absolutely perfect, that you are going to have a hard time making the cue ball go forward, let alone, trying to pocket something or put spin on something.
It's actually a great training tool if you want to straighten your stroke out.
Just see how many balls you can run like this.
Then rethink the question about rubber a rubber tip.
When I visited Tony Scianella's shop last year he asked me if I knew why tips were made of leather. I said "Duh.....tradition?" LOL I had never thought about it.
He told me it was because of the compression that leather allowed. It allows the tip to stay in contact with the ball longer than rubber or similar materials. To prove his point he did the very thing Superstar mentions above with a big rubber band over the tip of a $20,000 Black Boar. The results were both entertaining and enlightening.
<----wonders how a super duper high tech foam would work?