James, one has a manual thumb safety and one doesn't. Some people prefer no safety for concealed carry and some people prefer to have one. Just depends on how you feel comfortable carrying it. Hope this helps.

Thumb safety is just that an external safety

James, a manual thumb safety is just that, a safety that you manually switch on & off with your thumb. You cannot fire the gun if the safety is on. No safety means there is no manually operated safety, you can fire the gun by pulling the trigger at any time. The gun also has some built in safety features, whether it has a thumb safety or not, to prevent the gun from inadvertently firing. 1- Trigger Safety. The trigger safety serves the same kind of function as the manual safety. It must be in the Fire position to fire the pistol. With a trigger safety, the safety moves to the Fire position when you press the trigger. 2- Striker Block. The striker block interferes with the forward travel of the striker until the trigger is pulled. Like a trigger safety, pressing the trigger moves this safety component from its “safe” (blocking) position to its “fire” (free) position. Have a great day!