These are just my opinions regarding the two movies compiled together. BEWARE SOME SPOILERS!!!!
Weirdly enough, I like Emma Watson's speaking voice better than Paige O'Hara's (though Paige is definitely the stronger singer), and I think that's probably why I even like 2017 Belle slightly more than the 1991 version. Emma Watson's voice is more down-to-earth while still being elegant and classy, fit for a magical fantasy. Meanwhile, Paige O'Hara's speaking voice sounds like, well...a bell (get it? cause her name's Belle). Paige's voice sounds too perfect which probably made the original Belle feel too perfect. But both are valid interpretations of the character, and I like that they played Belle differently.
Of course, the 2017 version still kept Belle's core character the same. Emma Watson feels very Belle-ish and I couldn't imagine another actress for that role. Even though Paige O'Hara definitely wins in the singing department, I'm glad Emma Watson brought another interpretation to the songs. The British accent is better suited for BATB and made it seem classier. Emma Watson has that sort of quiet elegance and magic that makes the fairytale feel like a fairytale.
The voice acting/singing is still better in the animated version. Ewan's McGregor's voice acting as Lumiere isn't that great. While Emma Thompson sang decently, no one could ever beat the Angela Lansbury's perfectly nurturing and iconic voice. Chip isn't as cute in the live action. His voice is too formal, elegant and grown-up imo. Overall, the music/singing is better in the animated version.
The visuals were a hit and miss. Some of the scenes were beautiful while others looked shabby. I'm not really a fan of CGI, so I didn't really like the castle exterior, the Beast's design, nor the design of the enchanted furniture, which is too intricate. The simpler designs in the animated version brought out the enchanted furnitures' charm and made them cute and funny. I especially didn't like the design of Mrs. Potts. The whole point of having a sentient teapot is that the spout looks like a nose, so if you put the entire face on one side, then what's the point?
I like that they kept most of the characters' personality. Mrs. Potts is still warm and nurturing, Lumiere and Cogsworth are still the awesomely dynamic duo, with Lumiere being free-spirited and outgoing and Cogsworth being careful. The dog stool still has his dog-like charm.
The Beast in 1991 is better and more dynamic than the tame housecat in 2017. I could barely hear what the Beast was saying in live action. Most of the time he sounded like he was muttering (idk if this was on purpose)? I didn't really like the added backstory of the Beast's mother dying. That was too depressing and the blaming of other parents is just an old, overplayed trope. We could already assume that the Beast was mean for whatever reason. Besides, Beast's character arc of becoming a better person is redeeming enough in itself. We don't need to add the bad father and dead mother to try and justify Beast's behavior. I would rather they keep it a simple fairytale than try to make it complex. Maybe it was just to let Belle and the Beast "bond" over their lost mothers? Still, I didn't really like it. However, the scene where the Beast transports Belle to the past and see her mother was interesting, since Belle is the protagonist and the purpose is to show more of Belle than to "justify" the Beast's actions.
2017 Belle seems to like Beast more than the 1991 version. Maybe because it's easier to tell from a real person acting than showing it in animation. In the 1991 version, Belle's affections for the Beast seemed more mysterious. Either way, it's a good difference that they both have.
The Be Our Guest scene was more beautiful in live acton. It took over a year to plan and shoot, so no wonder it looked so good! But the singing was slow paced and felt like it dragged on. The musicality and faster tempo were better in the original. The scene where the wardrobe tried to dress up Belle was also beautiful and the library scene felt very fantasy-like. But I missed how Beast surprised Belle with the library in the animated version. The Gaston scene with the dancing on the tables was also good.
I also liked the little town scene in live action better and the addition of Belle teaching a little girl how to read. That was a cute scene. LeFou teaming up with Ms. Potts after Gaston left him was a funny touch. Belle trying to escape the castle by building a rope was also interesting.
In the live action, they turned the enchanted furniture into actual objects so the people in them "disappeared" which I found kind of scary, because it felt like the servants were dying, which isn't fair because they didn't do anything wrong. It sucks enough already to be furniture. Adding the actual enchantress was interesting. I think it suits to have the enchantress in live action, while the animated was better off without seeing her. I also liked how they cleared up in the live action that the Beast was not rejecting the enchantress because he was cautious of strangers, but because he was actually rude and mocking and laughing at her because of her looks.
My opinions on the wardrobe are reversed. The animated dresses are boring and overrated save for the golden ballgown. The live action wardrobe is better. But didn't like the live action yellow ballgown as much; it was just okay, not great. The ballroom scene actually looks kind of nice, but I might have done some things differently. Overall, the live action had some good parts, but I still like the animated one more.