Will probably edit this as I remember/think of more stuff, but these are my thoughts thus far:

Pros:
- Good variety of classic boards with updated soundtrack and graphics.
- Modernized mechanics means holding up to 3 items on all boards with a good variety of items to choose from, as well as more powerful items only appearing at the halfway point.
- Everything moves much faster. You can speed up AI players and skip watching their item/duel mini-games. Longer cutscenes can be sped up by the player who initiates them.
- Item spaces and duels now select from a variety of games rather than a single one that fits the level theme.
- Online is here with a much more stable connection than Super Mario Party, and has matchmaking with randos. Although I frequently do still get one player disconnecting during a match, at least it doesn't end the game for everyone like Super Mario Party did. Edit: Ok it's actually getting really annoying that in a 4 player game the tendency is that one player will leave.
- For the most part, a great selection of 100 mini-games. Though who was asking for the return of Bowser's Big Blast and Honeycomb Havoc is beyond me.
- You can view potential star locations on the map and board.
- You can see how many spaces to the star and what space you'll land on in each direction of a crossroads without opening a map.
- You can make Wario say "Oh Baby!" ad infinitum.

Cons:
- Wario no longer says "Oh my God!" or "Oh I missed!"
- Peach no longer says "Bitches got it!"
- Penguin buttholes REMOVED!
- Fun costumes from Mario Party 2 gone.
- An abundance of luck spaces changes the economy drastically, making it much rarer for a player to not be able to afford a star. This could be good or bad depending on your taste.
- The custom dice blocks from Super Mario Party are gone. I'm sure most players won't care about this, but I really enjoyed the added strategy they brought to the board game part. It's much more engaging to think about the odds of your rolls and watch someone succeed/fail at them when they have more influence than one 1-10 dice plus items.

- Bizarre online design choices such as:
- No punishment for quitters.
- Once you start searching for a lobby, you can't leave aside from waiting out a 90 second timer or quitting the game.
- Despite this being a collection of boards from 1-3, which all defaulted to 20 turns, online defaults to 15 turns, which makes it difficult to find matches outside of that.
- Can only matchmake with randos while playing alone.
- Lack of a ranked mode makes skill levels vary wildly.