If Edmonton had the depth to play McDavid, Draisaitl & RNH separately like Pittsburgh did with Crosby, Malkin & Staal, then they would, since obviously that would be better. But they can't without compromising the effectiveness of their top-six. Guys like Cooke, Kunitz, Guerin, Dupuis, Talbot etc. may not have been sexy names but most of them played 1000 games or close to it because they were very effective in their role and several were sought after by contenders. Even guys like Sykora and Satan played 1000 games and were getting healthy-scratched. Edmonton has guys you wouldn't take on the waiver wire getting regular minutes.
The Pens forward depth may not be great, but most of them could individually crack a stacked forward group like the 2020 Lightning, even if the Pens are worse as a whole. The Oilers have five, maybe six if I'm feeling generous that could crack Tampa's roster. While the roster is slightly different, the 2010-11 Penguins with Crosby, Malkin & Staal all missing half the season were able to finish tied for 3rd in the league and take the Lightning to 7. Meanwhile the Oilers went, like, two years without winning a game where McDrai were held scoreless. The Penguins depth could reliably keep the ship afloat, the Oilers depth cannot.
Sure, they couldn't move the puck for shit, but they didn't inhibit 87 & 71 from doing their thing or sewer you when they were on the ice with the bottom-six. They (and Orpik) were also guys contending teams wanted to add either in free agency or at the deadline. They're not world beaters, but you know where you stand with guys like that because they play within their limits. A lot of Leafs fans bitched about Hainsey, but he's an easy guy to play with because he's reliable, there is some value in guys like that. Larsson plays along those lines as well, but the other Oilers are a bit hit or miss. I don't think the difference is huge, but if both teams had missed the playoffs and were deadline sellers, the Pens D would attract more interest.