I agree Contador 2015 was better than Bernal 2019 in the final week. But Landa was stronger than Contador in the mountains even without Finestre stage.
That's not quite my recollection. Contador had taken back three minutes on Aru and four on Landa with his Valdobbiadene exhibition. He went way too hard on Aprica (his toughest stage ever according to a recent video) and after that, he clearly faded, bar for the tactically beautiful attack over the top of Monte Ologno with Hesjedal.
Honestly, I'd say they were both similar performances, down to the final margins. Bernal was a lot more solid overall, and in the third week, only losing time to Caruso on that last stage, and gaining time on Yates over the third week. Both of them really made their mark on the race with attacks over the top of climbs, Bernal on Montalcino and over the Giau, Contador over Monte Olongno and the Mortirolo -although even on that stage he lost time to Landa.
You can say the difference was that while Bernal could count on a strong team to shepherd him on the final week, Contador could count on the huge margin he took in the ITT and on that attack to Verbania. But over that final week, he looked a lot more up and down than Bernal. While Contador lost a roundabout 30 seconds on the hills to an inconsistent Aru on a couple of minutes on Landa, Bernal lost 30 seconds on the (down)hills to Caruso and ended up gaining time on that third week against an inconsistent Yates. Yeah, Dani Martinez had a lot to do with it, but while Bernal actually outclimbed Caruso on the last two MTFs to Alpe di Mera and Alpe Motta, Contador shipped more than a minute to Aru on both Cervinia and Sestriere.
And about the teams, Contador's Tinkoff squad faltered hard, but that was a team that featured Roman Kreuziger, Ivan Basso and Michael Rogers for high mountain support, which was then quite the lineup. I don't think they were that much less well-regarded as grimpeurs than Martinez, Castroviejo and Narvaez. Bernal was supported by a strong team but had no issues pushing the pace himself when he needed to, and played a tactically perfect stage to Montalcino, driving the pace early himself and allowing EF to push the pace before bridging up to Buchmann and riding hard to the line. Contador, perhaps because of the team itself (though both Tinkoff and Astana were very well-funded teams back then) and perhaps because of his early experiences with Bruyneel and HWMNBN, never quite leaned on his team quite the same way as Bernal is learning to.
On the flip-side, perhaps due to his back issues or due to some other physiological limitations, Bernal, despite an eerily similar build, has not taken to time-trialing as well as Contador. Without that, it's hard to imagine Egan coming close to Alberto's palmares, especially given the rise of Tadej Pogacar. However, in other ways, like the tactical nous, the positioning savvy, and the aggressive way they race, they are, to my eyes at least, remarkably similar. And this year's Giro does remind me quite a lot of 2015 bar for a more composed (and well supported) and ultimately stronger Bernal that final week.