I'm not sure about overall safety but, for me, I feel safer on a motorcycle.
I"ve been riding motorcycles for 50+ years and bicycles for 20. My experience is that you are much more in control of your own destiny on a motorcycle than on a bicycle. Motorcycles provide the ability to place yourself better in relationship to threats. You have the ability to flow with traffic or accelerate away from uncomfortable situations. Motorcycles usually have two decent mirrors so it is possible to keep better track of your surroundings. If you choose you will have much better protective clothing while riding a motorcycle. You are more visible and the noise of the motorcycle (hopefully not too much noise) allows people to be aware of your presence. I believe a person is at much greater risk while learning how to ride a motorcycle than while learning how to ride a bicycle but at some point that reverses.
Anecdotally, I have lost 8 friends to bicycle accidents over the years and one to a motorcycle accident, another 2 friends were paralyzed while racing motorcycles. Two of the friends that were killed on bicycles were lifelong motorcycle guys. Almost all these deaths were caused by being run over from behind. While a couple of the bicyclist were run over at night most of them were killed during the day.
All that being said bicycling will keep you healthier than motorcycling. Bicycling also makes the motorcycle experience better.