I like my M&P full size a lot, but I've never messed with one with a safety lever, so I don't know if it is one like the Beretta's where it is easy to accidentally engage when performing a reload, or one like the 1911's that is easy to activate with a good high grip on the gun. I try to avoid stuff that increases my chances of getting killed, so I opted for the one with the trigger safety only. Safer that way IMO. I would definitely recommend getting hands on any external safety handgun before you buy and doing some dry fire and reload drills to see if there are any accidental engagement issues.
This...and you can add a safety later if you Really need one
(and get rid of that dang mag safety...8) )