Any comment about this from those who played both games?
Because from what I remember, Unity was largely disliked/ignored on release.
is this video made to look shadows look bad?
Eh, that video goes out of it's way to make Shadows look bad IMO
Unity had a bunch of weird contextual parkour issues, just like literally every game in this series (seriously, every one has had assassins not do what I wanted them to do at some point, but Naoe is doing it with less frequency so far). Unity had a good sense of momentum due to animations, but the parkour itself really wasn't that much different to previous games. Still, IMO it had the best parkour in the series, until now.
Shadows has objectively better parkour. Naoe has more variety in animations (tons of fun vaulting, hurdling, sliding, and flipping animations), has that cool dedicated diving button, has a grapple for swinging and scaling, and she's significantly quicker. There's also more variety in objects her animations work on, vs Unity that has a few contextual rails you can hurdle, and some copy pasted Y trees for you to stand on (it benefits from one of the more homogenous settings we've seen in the games, which is more of a negative). In a single small slice video, it's easy to make Unity look better. It's not.
Also, like Rafter pointed out, Unity is one of the games that killed the old school style of AC with Syndicate. It's overrated by purists these days. Still, I give it props for actually trying to focus on stealth and being the first game to give us crouch stealth. It also still has the best assassin robe customization in the series IMO, so it's not bad. Shadows is infinitely better in all respects except customization.