Persona 5 Royal is still my favorite, but I loved that they brought a lot of the style of that game (mainly the art style and direction) to this one. I've never played the original Persona 3, but other people have told me it stayed pretty true to the original, just with more quality of life things. The music is terrific as always, and I loved the voice acting (people who played the original told me many of the characters' voices are much better in this one than the original, at least in English).
Tartarus is similar to Mementos in Persona 5 Royal, although I don't think it was as good. They give you a special clock that allows you to catch other character's XP up to each other, however, I had more trouble finding and proccing this special level up clock than finding Jose (didn't enjoy trying to proc him either).
The ending was satisfying and brought tears to my eyes (be sure to have a tissue if it's your first time like it was mine!).
Koro-chan is my favorite character and teammate. <3

This was great fun! Loved the new characters and seeing the old ones from the first game. I still think the first one was a bit better, but this one had my favorite somnium where I got to do a chef battle and another I got to gather pokemon to battle! As usual, the story is very well written and the voice acting is fantastic! If you love the first game, you should definitely play this one! I don't think you need to play the first, but I would highly recommend it since there's a LOT of references and running jokes to it you would miss out on get if you hadn't played it first.