The idea that the Colt Commander and M39 weren't developed for the 1954 tests seems to fly in the face of the fact they were specifically designed and submitted for consideration. Colt knew the Commander didn't fit the spec for 9mm but in most other regards it was appropriate. They had worked with Alcoa on forging aluminum frames for manufacture and as a result could get the weight down. S&W got in the game somewhat later but again, submitted guns with X serial numbers to the government for the express purpose of testing them for the Trials.
As for their performance the final reports documenting the testing at ranges and labs have remained out of sight. We don't know how they did. But we can look to the historical trend and say that the double stack Model 459 was introduced in the 1984 trials and held up well to the Beretta. When SIG was allowed to submit the P226 then repeated trials were conducted and it was the Army's decision without substantiation or any documentation that the Beretta was the final choice.
Two things came out of that decision, first, that the Air Force proposed the test all along with a desire to buy Berettas, and second, word came out that Italy made the suggestion that if we liked having a refueling station in the Med for the fleet, and an Airborne Brigade there, then Beretta was the obvious choice.
Regardless, the M459 performed well and had reliability that nearly matched the Beretta. It was, however, part of the newer emphasis on auto pistols for mil/LEO and after the tests S&W swung into much higher production as many departments purchased them in the changeover from revolver to auto pistol. Of all the contestants it could be argued S&W was the best design - because it continued to be tested and specified by hundreds of committees and jurisdictions across the country and became the finalist. It took the less expensive Glock and some disreputable negotiating tactics to intrude in that market. Some departments to this day still use the S&W 3Gen and won't consider any other.
Is it good? I don't read of any other auto loading pistol that will cycle empty cases and chamber them, given that may just be fan boy talk. But I've done it with mine. I need to expand that test but it requires owning all the others. Testing guns is expensive, and the test standards and protocols are critical in some areas. During the '84 tests it was noted 1911's were drawn, used, from armories and shot with used magazines, compared to the submittal guns tuned at the factory new, with new unissued mags. That happened with the M16 in another test and even Congress threw a red flag on that play. The details of how to test a gun can be influential to promoting one over the other - it is in fact exactly what is being done. What we don't know to the best of our abilities is what tests are actually realistic. For the most part nobody tests carrying the gun for 9 months with the same bullets in the magazine, the first constantly being rechambered, and being largely left to collect lint in the holster as it's just another part of the bearer's wardrobe. Nope, the normal tests are burying it in the mud - nobody deliberately does that in combat, it's incidental and we accept it will cause malfunction. They test it in freezing conditions, but it I was standing in freezing rain, sleet, and snow with the gun exposed, I would expect it to jam. They even test it underwater, I just wish they would have those testers be the rank of O-4 and above diving into the pool. That is who will use it.
Which is the real point of Army testing and the link does explain it right out in print - handguns are a secondary weapon, nobody goes into combat with them as their MOS primary working tool, and they aren't considered a major need. Everybody already gets a rifle if they need it. The pistol is just a peacetime accessory or used by those who can't be burdened with the bother (although some General Officers did carry rifles near battle zones.) For the most part, a token of rank or authority so that others will know they are empowered to do the job they do.
For the most part - if it's a handgun submitted for Trials and also has a large LEO population using it, it's good to go. Since everybody has to use it, it fits the majority of users. It operates in a manner consistent with firearms in general - note in the link the HK P7 was submitted but no dice here. If anything in the last 45 years the main items of change have been caliber - type of trigger control - and costs. The guns themselves still use barrels, have triggers, magazines, and sights on top. Pretty conventional and the pattern used since before the turn of the 20th century. Like binoculars and revolvers, we got the state of the configuration pretty early, and since then it's been more to finesse the details than any overwhelming game changing new innovation. It's still a handgun.