AFAIK Sac is not a sequel nor a closer adaptation, but an alternative timeline.

I grew up with the original movie that I watched at the cinema and never developed a strong attachment to Sac for that reason, it is good, but IMO it's not better than Oshii's version, on the contrary it lacks the poetics and the dreamlike aspects of the 1995 work.

p.s. Oshii also directed "Urusei Yatsura Onrī Yū?" which is IMO the best Urusei Yatsura movie even though it doesn't closely follow the manga, exactly because of Oshii talent with the dreamy stuff.