My Shield is for deep cover concealed carry, namely, when I wear a suit or formal clothes with a tucked in shirt. I want to be able to take off my sport/suit coat, like others in the room, and be comfortable.
I have used Thunderwear for almost 20 years. It has some drawbacks, but having a well concealed handgun, spare mag and a fixed blade with me all the time outweigh the disadvantages IMO.
It is a comfortable and secure form of carry, very similar to but deeper than carrying my FS RMR'd M&P 9 AIWB when I can wear a covering garment, which is most of the time now that I am retired.