Accurate
Don't know which had the most "mechanical accuracy". I've owned, and still own many very accurate pistols. I can say that the pistol I am able to shoot the most accurate of them all. Is the FN Tactical .45 with the Trijicon RMR. This pistol is capable of one hole groups at 15 yards - if YOU can do it. You really could shoot squirrels in the head at 25 yards. I do not remember ever shooting this pistol, without people in the lanes beside me, asking what I was shooting. From a rest it is simply amazing. I have 3 pistols with various micro red dots and I shoot them all more accurately than iron sights.
I suspect I have pistols that are as mechanically accurate that do not readily accept a Trijicon RMR etc. The Les Baer Monolith Heavy is one, very accurate but has no red dot. If you are speaking of .22 pistols, not carry handguns, I have an early Browning Heavy Barrel Target from the 1970's that is as accurate as anything I've owned. The early Models were hand fitted, hand rifled, chambers hand fitted, true Target Trigger. The new ones have none of these things - they just look approximately the same.