"Neither the slide or barrel are rigidly attached to the frame."
Correct, but it's a 2-way street, Doesn't matter if you use a slide mount or a frame mount. The bbl isn't attached to either 1.
"Point is, one systems disrupts the sight picture far greater than the other."
The sight picture might be disrupted more but the shooter will never be able to tell the difference. For most it's easier to pick up on the frame mounted red dots. Call it muscle memory or whatever you want. Shoot countless 1000's of rounds using a standard front/rear sights. It's pretty much seamless to use a mini dot sight mounted where the rear sight used to be.
When using frame mounts you have get used to the difference in the balance of the firearm along with a different sight alignment to get on target.
I own both slide mount and frame mount mounts for the 1911's. I much prefer the slide mounts over the frame mounts. They both are equally accurate when used correctly. But canting is more of an issue with the frame mounts simply because the dot/scope is high in relationship to the bore then the slide mounts.
I've used mini dots on pistols for over a decade, mainly 22lr's (S&W 41 & marvel conversion kit #1 for the 1911).Same goes for the tasco pro-point red dots on s&w's 629, 586, 617. Accuracy has always been acceptable enough to allow me to not only compete in the shooting sports I was using them in. They allowed me to be competitive at a high level.
Accuracy means different things to different people. Several weeks ago I did some testing with the 1911/45acp pictured in post #8. I've sold off a bunch of molds for the 45acp's and I'm down to 3 bullets that I cast for the 45acp's.
Left:
A special order cramer mold from the 1950's. It cast a bullet similar to the h&g #130 but it's a hollow based bullet. It's hollow based because it was designed to be used in the surplus 1917 pistols that were chamber in 45acp and known for their oversized cylinders & bores.
Center:
Mihec mold, their version of the h&g #68 (actually #69/isn't bevel based) that happens to be hollow pointed. The hp is for accuracy and it will out preform the solid nosed version of the same bullet (mold has hp and solid nosed pins). But it takes the 50yd line to bring out the difference which isn't much.
Right:
Another mihec mold, this bullet is their version of the flying ashtray.
I have a bunch of clays powder laying around, always stocked up on clay and bullseye powders. A little goes a long way and if you can't find an accurate load with either powder, somethings wrong. Looking at the reloading data I settled on 4.0gr and 4.3gr of clays and those 3 bullets pictured above. I was looking for a general purpose range play/blammo ammo that would push those 3 bullets pictured above in the 800fps+ range. Simply wanted a load for paper/bowling pins/steel/beverage cans/etc that would hit with a little authority but would allow for extended periods of range time without getting fatigued. Made up some test loads and went to the range and setup a pistol rest @ the 50ft line and did 5-shot groups/test with the different load/bullet combo's. This is what I ended up with.
The 4.0gr loads of clays were worthless. The 4.3gr loads on the other hand were what I was looking for. The mihec #68 and the cramer held the 5-shot groups in the .7xx" and the mihec 200gr hp 1". I rattled off 5 shots with the mihec 200gr hp (top right target) 1 handed bullseye hold in 25/30 seconds testing recoil/recovery times. Didn't do very well, 2" with a load that held 1" from a rest.
Anyway either mount will work, either mount will be accurate. It comes down to what the shooter is comfortable with and their ability to use that equipment.