The Islanders definitely had the best beards.
Just to muddy the waters some more, in '81 the baby Oil swept the greying, Dryden-less, Bowman-deprived, Canadians 3-0 in the first round. In Round two, they met the Isles and took them to 6 games, New York's biggest challenge that year.
In 1981, the Canadians were only two years removed from their last cup and the Oilers were 3 years from their first. The Islanders were going for 2 out of 4. Dominance or "dynasties" sure don't last long.
I think all three teams were pretty close
Sorry, but that's equivalent to saying the '85 or '86 Islanders should be compared to the up and coming Flames, or the Oilers in '92/93 be compared to those years Pens. Yes, the Canadiens sucked in those '81 playoffs. Their goaltending those years ('81-83) was atrocious. But remember in '80 the Habs under Claude Ruel, from his appointment on, dominated Central Red Army and had the best regular season mark after the half-way point. And that's without their HoF goaltender, HoF top-line center, and HoF coach from the previous year. If Lafleur doesn't have his knee wrecked in the opening round, they're probably in the conference finals against Philly. Minnesota beats the Habs in 7 because of a last minute brain cramp by Herron, but they're also playing that game 7 w/out all of those mentioned above, as well as Savard, LaPointe, Risebrough, and Mondou, due to injury. 1980 "Drive for Five" Montreal is a skeleton team, that only got thinner the following season.
Do you really want to compare dynasty's power from what-ifs? Without the WHA 1970s Montreal has a Big Four, with JC Tremblay(WHAs top D in '73 and '75), Frank Mahovlich retires a Hab, Marc Tardiff doesn't become the WHAs all-time leading goal-scorer, Rejean Houle's superlative checking and opportune scoring is there for another four seasons, and HoF Rod Langway starts his NHL career a year sooner. Sorry, but Montreal's organizational depth throughout the 70s was jaw-droppingly good, and the fact that they could dump a guy like Jimmy Roberts, a Bowman favorite, who'd appeared in 9 Stanley Cup Finals, a winner perhaps analogous to Mike Keane, as superfluous, and win another two Cups, is testament to their greatness.
I'd also note that as awesome as the Big Three were, it also undervalues how good the other Habs D-men were. Nyrop, Engblom and Langway were all top 2-4 D-men on probably any other teams in the league, outside the Elite (Boston, Buffalo, Islanders, MAYBE Philly) and Bouchard was a wonderful hard-rock, stay-at-home, defenseman that any coach would've loved to have that whole decade.
People can ***** about that Habs team playing to lesser teams due to the WHA, but they found a way to make Don Cherry a commentator, look better than Central Red Army both times they played ('76 and '80), swept the Bullies, and made just about every other team, with the possible exception of Buffalo, look like after-rans (see Toronto '78 and '79), bespeaks their dominance.