Since nobody has mentioned for 3DS legal stages, for something like Anther's Ladder netplay, here's an opinion on those!
(Again, this is 3DS, as I have little access to WiiU, and while I'm aware there's a very small tournament presence, there is still some)
Battlefield - It's a neutral map, and platforms are great for Corrin.
Dreamland 64 - It's a counterpick map, but still got platforms! Wind can be an issue, but not all too much since it's not unpredictable.
Arena Ferox - Counterpick map, inconsistent platforms, but there's some funky stuff that can be done here. My personal favorite is the setup where there's a hanging platform over the left ledge shaped like a ^. An up-b at a decently high percent can stage spike people off of the bottom of the platform, right off the stage. It's a pretty good map in any of the platformed variants.
Yoshi's Island - Neutral map, single platform in middle that tilts, so that can **** with platform shenanigans, and create others. Floor is uneven which can greatly **** with ledgeguard locations and side-b in general. Sides can help recover, but same with enemies.
Duck Hunt - Counterpick map, uneven spacing of platforms and it's just odd. It's not a bad map by any means, but can still have odd benefits and bonuses. If you can manage pulling your enemy into the tree, you can kill up the top rather easy, but other than that, the roof is rather high, the sides can help you recover, but help other characters as well.
Prism Tower - It's just a stupid counterpick map, I'll be honest. It's got walk-offs at the beginning, no platforms some times, platforms over center stage other times, platforms on the sides of the stage others, a shrunk center stage at points, and single platforms over center some times. It's got a lot of changing that Corrin can't really take advantage of. Especially the side platform portion. That part's just stupid.
Final Destination - The year is 20XX and fox ha- Corrin just can't really do well here. No second option of recovery as there aren't stage walls, no platforms to get enemies onto, depending on the opponent, it can be hard to close in, also due to lack of platforms, so on.