I've noticed several times in Star Trek that the penultimate episode of a season is better than the actual Season Finale. More times than I realized. Which makes me wonder, "If they had a strong episode here, why couldn't they have ended on that note?" Or at least of have had the episodes swap places.
Seasons where I think the penultimate episode was better:
TOS Season 1: "The City on the Edge of Forever"
TOS Season 3: "All Our Yesterdays"
TNG Season 1: "Conspiracy"
TNG Season 2: "Peak Performance"
TNG Season 5: "The Inner Light"
DS9 Season 1: "Duet"
VOY Season 1-ish: "Projections" (it was the penultimate episode filmed in S1, but it was held over for S2)
ENT Season 4: "Terra Prime"
That's a lot.
Seasons where I think the penultimate episode was better:
TOS Season 1: "The City on the Edge of Forever"
TOS Season 3: "All Our Yesterdays"
TNG Season 1: "Conspiracy"
TNG Season 2: "Peak Performance"
TNG Season 5: "The Inner Light"
DS9 Season 1: "Duet"
VOY Season 1-ish: "Projections" (it was the penultimate episode filmed in S1, but it was held over for S2)
ENT Season 4: "Terra Prime"
That's a lot.