I was trained on the 1911, and carried a M9 on duty. I purchased a Glock 19C, and a LCP. I sold them both in the last 30 days. Now I have a SIG P938.
Polymer vs metal: polymer can't rust, corrode, or wear down to a base layer. Metal guns these days have excellent finishes that are highly resistant, too. Polymer can assume complex shapes that are difficult to machine, and can achieve a singularly organic look. Metal guns are somewhat limited by the machining process and always have a machine like appearance. It's very difficult to modify a cast polymer part, it's easy to modify a metal part or even refinish it. A polymer gun that has aged from long use is basically a melt job with the external details worn, the metal gun aged from long use is said to have a patina, and collectors may even pay extra for it.
Strikers vs ? Must be hammers. Strikers are spring loaded firing pins held captive and released with a sear mechanism. They take up length in the slide and because of that are not compact. Strikers can be partially cocked with the trigger pull finishing the complete retraction before release. But, like bolt guns, they could be held fully back, cocked and locked like a bolt gun. Nobody is doing that, however. Hammer guns use a similar spring, but it's located vertically in the grip to actuate a hammer, which rotates the motion 90 degrees to a much shorter firing pin. The overall length of the apparatus can be the same, however, the hammer allows it to be much shorter at the slide, making the gun potentially lighter - or adding to the barrel length. A hammer fired gun can be cocked separately from the slide cycling, or uncocked, too. The length of the trigger pull is opposite, a striker requiring more travel to finish loading the spring, the pull of the hammer fired gun only that which is needed to trip the sear.
In the realm of battle pistols, a case could be made for polymer/striker guns overall superiority in harsh conditions against a plentiful enemy. The reality is that auto pistols are often more a symbol of authority, and their role is really limited to being a personal defense weapon - when a rifle isn't allowed to be chosen. In America, that means the pistol will likely be used at close range, in a very short timespan, with three shots or less fired. That puts the polymer, striker, double stack pistol at a disadvantage because of it's bulk, long trigger pull, and the unnecessary amount of ammo it contains. The metal pistol, hammer actuated, and traditionally single stack, then shows it's advantages as having the higher social ranking, a lighter weight, and easier trigger pull, enhanced with the safety of a trigger locking lever.
As a duty gun in a belt holster, the polymer gun has advantages. The metal gun with hammer works well as a small personal defense weapon with more variety of manipulating the firing mechanism's states of readiness. Or, at least, that's the way I see it this week.