The safety wont make it any better unless it makes you more comfortable and you teach yourself to flip the safety without thinking. I truly believe that any weapon that is carried with a safety needs drilled with...A lot. In a high stress situation you will want to be able to flip that safety and not think about it while your doing it. Nothing is worse that (God forbid) you have to raise your weapon and it don't do anything because you forgot to click the safety. Both pistols you mentioned are good ones. Either would serve you well. I'd probably lean to the M&P mainly for the back strap being changeable. I'm sure the Glock fan club will tell you all the ways a Glock is better than sliced bread soon enough.
If you decide on the one with the safety just practice,practice,practice. Many people all over the world use pistols with safeties. I carry a 1911 left handed that does not have the ambi safety installed. I am very quick and have the gun up with the safety off and am ready to fire as fast as anyone can hope to be. But I drilled it over and over for a long time. I still practice it a lot. I have some with ambi- safeties also. I practice with all my carry guns almost daily.
The best fit to your hand is the one to get. Remember..Everyone is going to have an opinion. but you are the one that is going to use this weapon. So you need to decide what is best...for you.