Without getting into a LONG description of the different actions mechanics:
Colt uses a system in which the cylinder is forced tightly into alignment with the barrel at the instant of firing. This system depends on the action being in perfect adjustment, and also accounts for the Colt's reputation for being a more accurate revolver.
Since the chamber is perfectly aligned with the barrel, the bullet enters the forcing cone without any distortion. The less distortion of the bullet, the more accuracy is possible.
The S&W, Ruger, Colt King Cobra, and all modern revolvers use an action that allows the cylinder to be slightly loose at the moment of firing. This allows the chamber to align itself with the bore.
The "problem" with this is, the aligning force is the bullet itself, so there is a slight amount of distortion to the bullet, and this degrades accuracy to some extent.
Because of the action design, the Colt action tends to "stack" or get progressively stiffer as the trigger is pulled. Colt shooters often use this to help "stage" the trigger by giving it a slight "jerk". This causes the cylinder to unlock and quickly rotate to lock. This leaves the trigger with a smooth, easy pull until ignition.
Many PPC shooters add rubber trigger stops to their S&W triggers so they can stage the trigger much like a Colt.
The Colt action is a more complicated action, with a non-obvious method of operation. It uses very small operating surfaces, and these must be in proper adjustment simply to allow the gun to work properly.
The Colt uses a single double legged spring to power the entire action. S&W and all other modern revolvers use separate springs to power the hammer and trigger assemblies. Neither is particularly superior to the other, just different methods of accomplishing the same functions.
Where the S&W is somewhat "better" is when the action is being "tuned" for match use. The separate springs allow the hammer and trigger tension to be adjusted individually, and this is easier for the pistolsmith.
Because the Colt parts that rotate and lock the cylinder are smaller than other more modern guns, the Colt's have somewhat of a reputation of getting "out of time".
In the classic Colt out of time condition, it's possible to slowly cock the action to full cock, WITHOUT the cylinder going into it's proper locked condition.
In truth, unless the action is badly abused or altered, the gun will fully lock up when the trigger is pulled, so this isn't as serious as might be thought.
Later Colt and most more modern revolvers have larger, stronger action parts. What this really means is that they will take more abuse, longer, than the older Colt action will.
Abuse of a revolver is "Bogarting" the gun by flipping the cylinder open and closed with a flick of the wrist, force cocking the hammer, or forcefully yanking the trigger in double action.
All this will batter any revolver to eventual out of time problems, it's just that the Colt doesn't stand the abuse as well.
A big advantage of the Colt action, is the fact that the cylinder notches are placed between the chambers where the metal is thickest, instead of directly over the chambers like on the S&W.
So, IN GENERAL, the Colt has better potential accuracy, the others have actions that will take abusive treatment better, with non-stacking triggers.
