Go with what you are used to. I don't own any guns with manual safeties. So, when I bought my Shield, I got the one without the safety. I like to keep all my carry guns similar in function so under stress they all work the same way.
Personally I do not like external safeties on defensive hand guns. Simpler the better in a high stress situation Im sure others will disagree with me.
The trigger on the LC9-S is scary light. The no safety version of that gun is crazy in my mind.
I got the non safety and regret it. If you slide the gun in the front pants pocket with a loaded chamber, you have a round waiting to go off pointed at you. You reach in the pocket in a hurry and pull the gun out and the trigger gets pulled before you clear your pants...boom, you just shot yourself. And if you think it can't happen, check out Youtube for the number of times cops have shot themselves with a Glock coming out of a holster. I prefer a safety.
This. I do the exact same thing. I've never been a fan of TS but I kinda like the one on the shield, small and stiff.I agree with RobzGuns. I disengage the safety when the gun is holstered so it's ready to go if needed. The safety lever is small enough and stiff enough it will not be re-engaged by accident. When I'm not carrying the gun, I engage the safety for that added bit of comfort.
Bottom line (from my perspective): You don't need it, but you may well find there are times you like having it. If you choose to carry the gun with the safety engaged, practice with it regularly to make sure you can disengage it under pressure, it doesn't fall under the thumb like a lot of other safety levers do.
Although I don't have much time with my new shield, I bought one with the TS. Seems like as long as I train with what I carry (weapon and ammo) I will be conditioned to switch the TS off.