I have been through several thumb safeties and here are just a couple of thoughts.
The Wilson is too narrow, short and sharp for my tastes. I used to like them a lot but that was before I had used anything else.
The STI that I bought is so far out of spec as to be unworkable.
The Gunsite low mount is great but only if this is the only style you use. If you have one of these and one of a more common configuration, its easy to get confused. In the "safe" position, it feels like the "fire" position of any other 1911. When the "S" hits the "F", I can see that this could be a real problem
I have settled on the C&S model, although, it looks pretty similar to the Brown. I like the contour of it and the width. Its just right for positive engagement without getting in the way.
As for ambi safeties, I don't like the Kings. Yes, I know this is what the Marines are now using on the MEU(SOC) pistol, but I can't stand them. They don't curve down. That means, when you go to rapidly charge the gun, it is VERY easy to catch the tip of your middle finger on the tip of the right side safety.
I'm not crazy about the Swenson style safeties as they always just seem fragile to me. That's a very small tab of metal under the grip panel to retain things.
I do like the new style Kimber ambi safety and I have one on my Springfield Operator. It uses a dovetail notch on a special hammer pin to retain it. It has a nice curve that prevents damage to your fingers when charging it. If I ever get another gun with an ambi safety, it will be the Kimber model.