Doomsday I was lead by prime Bob Lilly. George Andrie probably is the most underrated of all Cowboys. He was a great pass rusher. Jethro Pugh was a terrific DT. Willie Townes and later Larry Cole were good DEs when the game was played differently than it is now.
LB was where Doomsday I had a clear advantage -- prime Howley, Jordan and Dave Edwards. They were very active, smart LBs who forced a lot of turnovers. Howley was magnificent, and during the Golden age of MLBs, Jordan was one of the best.
The secondary had both prime Renfro and prime Cornell Greene, both of whom were outstanding. Renfro is the best DB the Cowboys have had, in my opinion. No disrespect to Deion, but he spent only a portion of his career in Dallas. Before a career altering injury, Mike Gaechter was a big-play safety. Dallas was usually short about one good DB, but Herb Adderly, even near the end of his career, nicely filled one hole.
Doomsday II countered Lilly with Randy White. Both great DTs, but I'd take Lilly by a thin margin. John Dutton was probably as good as Pugh, though likely not better. The DEs were more dominant, even taking Andrie into account. Harvey Martin was a sack artist, though Too Tall was probably the better overall player.
The LB corps wasn't quite as good, though Hollywood Henderson was spectacular and Bruenig was a solid player. Neither contributed as much as Howley and Jordan. And they didn't have a third guy like Dave Edwards.
The CBs weren't as good. Guys like Washington and Benny Barnes. Certainly there wasn't a Renfro in the house. But the safeties were amazing -- Harris and Waters -- and perfectly complemented each other. Harris was the best in the league, and Waters was a big play machine.
I guess I'd give a small edge to Doomsday I because Lilly and Renfro were Hall of Fame players, Howley certainly should be, and a case easily could be made for both Jordan and Cornell.
But Doomsday II makes it's own case with Hall of Famers White and Harris, and Martin and Jones who both should have a case.
Interestingly, both teams had a wildly underrated DE -- Andrie and Jones, respectively. Andrie would be remembered much differently if sacks had been an official stat during his career. Jones filled a different role than teams generally employ now. He was great against the run, tipped who knows now many passes and also controlled the screen game. He was a great, great player.
CB might tip the scale, and if Doomsday II had been stronger there, the Cowboys probably would have beaten the Steelers in one or both of the Super Bowls the two teams played.
So I am going with Doomsday I. But both were great defenses.
Landry felt that Lilly wasn't just the best DT but the best player in the league when he was in his prime. I tend to trust the judgment of the Man in the Hat.