They all have similar actions, the Beretta proprietary boxloc action with coil springs, a much more robust action than the Anson Deeley, and in my opinion, better designed.
I have dismantled many of them, and never found an unhardened part or one that was not properly squared and adequately finished where it counts. My local Beretta dealership has sold a few of these, never sold any parts for them, they never break it seems.
The 625 is extractor, 626 ejector, 627 glopped with sideplates, 470 and 471 EL are the later versions with minor variations in the locks and hidden monobloc joint, the 486 is a totally different action, needlessly complex in my opinion but round bodied and that is a factor for many.
You might find the 20g a little front heavy due to barrel thickness.
