My base is a 1911, cocked and locked.

If you know how to use a 1911, the thumb safety isn't a problem: you disengage it in the process of presentation: no extra time involved.

If you're a lefty, it's somewhat more time consuming


On the shield, the thumb safety adds nothing but it's absence isn't an advantage.

I suspect that most folks who buy the Shield don't have much handgun experience so the average consumer of this product hasn't mastered the use of a thumb safety

That said, the Shield thumb safety is pretty miserable and unpleasant to use so it doesn't impress me as a desirable feature

However, telling a jury why you didn't use a safety mechanism is tough going at best.

Just my opinion, of course.