Yes, the base rules are very close. There is some adjustment to accommodate slightly different ground/unit scales, but the general principle is the same.
Maybe there is a slight difference in complexity from game-to-game, again depending on scale. From what I can see, the 'Shattered Union' version is a bit simpler than the Revolution Games series, while 'A Most fearful Sacrifice' look marginally more complex.
I've been playing all the 'Kernstown' scenario's quite extensively and have pretty much now had my few queries on the rules answered., so I now feel very comfortable with the series.
I shall be whispering in ears that the 'South Mountain' game would be a very welcome Birthday/ Christmas pressie..............
“O Lord God, let me not be disgraced in my old days.”
'We few, we happy few, we band of brothers'