I think the difference comes strictly down to team success. Give Ovechkin a 6-team Canadian league and a dynasty team and I bet he has significantly more playoff success than he has been.
RS: Not even close, Ovechkin is pretty far ahead in this aspect (3x as many Harts, 3x as many 1st place point/gp finishes, 1 more Ross, almost 2x as many Rockets) - and he did all of this in a more competitive nationalized league.
Playoffs: Ovechkin has lead the Caps in goals in more post-seasons than Richard did (Ovi is tied for #1 all time), Ovechkin has also lead the Caps in points more than TWICE as many times as Richard did for the Habs (9 vs. 4) - only 2 players have done more (Gretzky and Howe). Both Ovi and Richard were the best playoff goalscorers of their era, and then one of the best (but not the best) point producer.
Ultimately, the gap in RS is much larger than the gap in the playoffs - and the RS is weighed higher in most peoples minds, since the playoffs are significantly smaller sample sizes, and much too dependent on team success.
I'd agree on giving Ovechkin the regular season edge. But I disagree with your playoff assessment.
If you take Ovechkin's rookie season (2006) till today age ~36 - he has 135 points in 141 playoff games, and 71 goals. Point per game of 0.96.
If I filter by players with 80+ games in that stretch, he comes in: 3rd for points (56 behind Crosby, 39 behind Malkin), 1st in goals (2 above Crosby, 7 above Malkin - less games though) and 7th in ppg (though, practically tied with 5th place) at 0.96 ppg - Kucherov #1 at 1.12, than Crosby 1.10.
Richard - if you take his rookie year (1942-1943) to age ~36 season (1957-1958) - so similar stretch as Ovechkin - he played 121 games, has 81 goals, 122 points and 1.01 ppg.
If I filter for 60+ games played in those years, Richard is first with 122 points (37 points above #2), he's first in goals with 81 (35 above 2nd place, almost double), and first in ppg (1.01, second place 0.95).
Richard also has 18 Game winning playoff goals (2nd place is 11), and his even strength points is also a huge gap (93 to 59 for 2nd place). Ovechkin is tied for 8th in game winning goals (10) in his years.
Maurice Richard also has 6 overtime playoff goals, which was the record for the longest time (Sakic has him beat with 8).
Richard very clearly has the much better playoff resume than Ovechkin. If you weight Regular season highly enough and playoffs low enough - it's fine to argue Ovechkin > Richard. I just don't at all agree with your characterization that they are close for playoffs. I know it was a different era with 6 teams, and Habs obviously were a strong team - but Richard was the biggest reason why, and he should get credit for his performances. Vs his peers, he does a lot better than Ovechkin does.
To take your bolded claim - it's false, because Richard is by far #1 point producer of his playoff era, while Ovechkin is not of his. And Richard has a huge lead on goals vs peers, whereas Ovechkin is just barely #1. Big gap for Richard