It's tough but from an action perspective ZSJL just has all the good shit. Watchmen is close to perfect overall but ZSJL although it has lower lows in terms of dialogue and story and actors (mainly flashfag being the problem and WW's first scene being kind of corny) ZSJL has better more satisfying action scenes and very visually gratifying visuals oveall in terms of the grand action sequences with the Old Gods and Darkseid/Steppenwolf.
It also helps that Superman has his dark kryptonian costume, it makes the journey from MoS to BvS to ZSJL that much more heartfelt and truly won.
I'm going to say that since ZSJL is part of a trilogy technically then put together as one cohesive story MoS+BvS+ZSJL is better than Watchmen director's cut.
As individual films standing on their own without having watched MoS or BvS then Watchmen takes it.
If the Watchmen movie were identical to the comic