I think that the thumb safety on the Shield is a particularly good idea. This is a gun that will be carried for years and likely never used. The operator is far more at risk from handling error than not being able to deploy it instantly in an emergency. Besides, with some careful training, good muscle memory can be developed to present and fire the Shield safely and in a very good speed. Big secret to that small little thumb safety is to press the thumb hard into the slide while working the safety.

For those who want to use the Glock, there is a very good technique to ensure 100% safety re-holstering in blind areas. Use a "clip on" IWB holster and when re-holstering, remove the holster from the belt. Then holster the Glock into the holster in front of you. Now take that IWB holster with Glock inside of it as a unit and replace the holster/gun unit into your waist band. Takes very little extra time, but offers complete control and safety. This will of course work with any striker weapon that does not have an external safety, like the non-safety M&P.

These are only my thoughts on the matter of external safeties. I am always open to other ideas to consider, so please do chime in if you have a good idea that has worked for you. I really liked some of the past posts stating that different people have different preferences.