The best of the ambi safeties are the Wilson Bullet Proof, and the EGW.
These are machined from bar stock instead of being MIM or castings, and have a far superior manner of locking the parts to each other and the frame.
These use the superior method of a special hammer pin that locks the right side firmly in place.
The old Colt type that uses a longer sear pin to lock the right side in place is no longer available and the later version was poor quality and developed looseness or just broke in the dovetail joint that interlocked with the left side.
The original ambi was the Swenson type that has a "paddle" that fits into a notch cut in the right side grip to hold it in place.
This type has a bad tendency to allow the right side to move out from the frame and disengage from the left side, and again for looseness or breaking of the dovetail that joins the two halves.
The Kimber/King's type uses a longer notched hammer pin to lock in place and this is better then either the Colt type or the Swenson type.
Unfortunately the various makes all seem to use MIM or cast steel, and again, the dovetail joint that locks the two halves together is not as strong as needed.
The Wilson and EGW use a far better interlocking system that's much stronger than the other types.
Also, these are mirror images of the left side safety where many other types have a right side that's much smaller.
Some people just prefer the same size mirror image for cosmetic reasons.
Ambidextrous Thumb Safety, Tactical Levers, Bullet Proof®, Blue
shopwilsoncombat.com
The Wilson is available in blued or stainless and with wider pads.
This Ambi Fits (Fitting Required):Single Stack 1911sDouble Stack STIs (With STI Hammer Pin)Patent Number: 10,126,086 B2 Watch our install video here!
www.egwguns.com
The Egw is also available in blued or stainless.
In all cases the paddles can be cut down if you prefer a more compact safety that has less chance of being moved by a holster.