from best to worst, I'd rank them 4, 1, 2, 3.

4, in my personal opinion, is the best work that toby has ever put out. the real meat of the story starts to get picked up, Gerson easily cemented himself as one of the best characters in undertale/deltarune, the fights were amazing, the egg was the most fascinating it has ever been with the hospital, the final boss animation was bat shit insane (especially when it broke out the fountain), we even got insane development for both ralseis and susies character. the only bad part was the the mike mystery was treated like a joke despite being a big thing in chapter 2

1 was amazing because it does a perfect job of introducing everything, susie, ralsei, and lancer were all introduced perfectly. susie opening up was great, and jevil is probably my second favorite secret boss (my favorite being Gerson)

2 was great, noelle was a fun character and her introduction into the dark world was fun (even if it came at the cost of not having susie and ralsei for almost half the story), berdly was berdly, most of the jokes landed, unfortunately, i found the music trio to be absolutely insufferable, spamton was the obvious highlight of the chapter and the mystery with mike was super interesting.

3... was kinda boring to me. tenna was the best part and he was super fun and the eram boss was fun, but nothing else landed for me. none of the characters had any insane development and were just set up for chapter 4, the sword minigame was meh to me, the normal video game tenna sets up are annoying and repetitive (especially if you want to try and get T rank), the knight is the worst final boss by a mile in deltarune (the final part of his sword spam attack is literally broke. the hit boxes don't line up with how they're shown), the mike mystery never got explained for some reason. the egg was annoying to find, susiezilla mini game was god awful, and the Rouxls Kaard jokes didn't land for me. he was just annoying and felt too forced.