All three of these films are ten out of ten classics!
The films plots and Styles are all very different yet there are similarities. All three have big casts, Magnificent 7 has Steve Mcqueen, Yul Bryner and many more, Big Country has Gregory Peck, Charlton Heston and others while The Long Riders has David carradine, Dennis quaid and more. All three have great music scores, The magnificent 7 and the Big Country's being two of the most famous themes of all time, and Ry Cooder does a great traditional score for The Long Riders. All three films are so good that you could name any one of them as a favourite western of all time.
The Magnificent 7 disc comes with the Special edition extras the other two film have no extras. The 18 certificate is due to the bloody violence in The Long Riders.