When I get the game I will post my opinion, but from the pictures I saw,
Toad Road: Looks great and has good scenery.
Factory Level: Looks pretty nice, snot very scenic but the conveyor belt thing looks interesting.
Boo House: Haven't seen much of it, at all.
Blooper Beach: Looks good, haven't seen much but looks good.
Magma Mine: the concept sounds really good, I'm personally looking forward to this one.
Bowser Level: Looks sweet from the picture, haven't seen any gameplay but t looks great.
DK Level: don't have much of an opinion here, but Diddy's there so that's pretty cool.
Sorry if I didn't write the names properly, on iPad.
Toad Road: Very mario-esque, a good start and not too dangerous
Boo's Horror Castle: reminds me of ghost houses which aren't my favorite
Blooper Beach: You can go in water!
Magma Mine: The lava makes it more tense unlike other games.
Bowser Station: Too similair to warped orbit.
Toad Road: Very straight forward, but good for beginners
Bob-OMB Factory: Introduces a couple of split path things which was a nice touch.
Boo Castle: Introduced things following you. Wasn't very easy though. But it was well made.
Blooper Beach: Great level, Added more onto the chase after/getting chased formula. Also the strategy involved with setting up opponents for mini ztars.
Magma Mine: Great idea and the whole magma rising spaces can really screw over your opponents.
Bowser Station:A great looking level and the best captain events, but seems... Lacking.
DK Jungle: A great place to grind for party points. Also, a nice atmosphere and the banana thing was good. Seemed lacking like the bowser one though.
I'll go with Blooper Beach. Usually I hate water levels but this one was well made.
I have yet to play Bowser Station and DK's Jungle Ruins but here are my opinions for the other boards.
Toad Road:Simple, good for beginners but fun if you don't want a way to lose half of your mini stars
Bob-Omb Factory:The Bob-Omb Gimmick is good and is fun seeing others getting blown up. Liked the Captain Event
Boo's Horror Castle:It's fun trying to make the boos catch up when they are far away but it's not fun at all when you are caught. Like how you have to roll a certain number at the end of the board to move on. Least favourite so far due to how frustrating it can get
Blooper Beach:I like the idea that landing on event spaces would turn all Mini Star into Mini Ztars as it makes the game exciting.
Magma Mine:The Which Way Wheels where a good gimmick here as it makes the game get very hyped because you want them to land on a Magma space and get burned.
Bob-Omb Factory and Magma Mine are my favourites so far.