Marth has never, and should never, HAVE to sweet spot. Like has already been said, up-B onto stage should be a viable option, it just needs a little end lag/landing lag and it'll be punishable.

Not having to sweet spot isn't the problem with the move lol

I guess I´ll just bring in another point: Do his specials have a tipper bonus? DS has one, but what about the others?

only nspec and upb

If Marth sweetspots the ledge in Melee he can get gimped by the Marth Killer. Clearly sweetspotting the ledge isn't an option here.
http://i.imgur.com/6WrHuTl.gifv

EDIT: Speaking of the Marth Killer, I just tested and it works in SSF2. The fall off part is easy, but the character doesn't recover from the fall off in time to grab the ledge. They do have time to hit Marth with a fast aerial OR snap to the ledge if they have a move that lets them, like in this example: https://gfycat.com/IncompleteVacantBalloonfish

cool gif at the end there, but marth players almost always recover by hugging the stage as much as possible when the option is accessible to them. In the gif you made, the marth player is too far away from the ledge to recreate what people usually do (that, an it looks way less safe lol). is it possible to do the Marth killer when Marth up-specials closer to the stage?

There is a distance that Marth can sweetspot from below so that he doesn't hit the shield but still will grab the ledge, this occurs because Dolphin Slash doesn't hit directly above Marth (even tho the animation says otherwise). If he hits the shield, then what happens is all based on how well the Marth sweetspotted. If Marth sweetspots even remotely well he snaps to the ledge first well before Fox would fall low enough to grab (only instant shine would do anything here lol), if he doesn't then what I found applies. That's on a stage like Warioware. If I do it a little closer on BF, and I get the same results.

This is all done through TAS tho, I don't think any human can pull off what I did in the first gif either. Fox has to fall for about 2 frames before he can side-b snap to the ledge, Marth tends to grab during this window if he sweetspotted at all. Not to mention that many characters just fall past the ledge and don't grab it at all like they would in Melee, so only certain characters can even pull this off. In terms of realistic inputs, Marth just grabs the ledge to early to do anything off of this
The conclusion being is that it is possible, but not practical oh the world of TAS

What competitive stages to you guys think Marth excels on or is there even a stage he has an advantage on?

FD against fast-fallers (watch M2K play to see why), and Yoshi's Story against everyone else (so you can get free combos off of platforms and tippers) IMO.

While I do agree that its easy to get tippers on Yoshi's Story it is even easier on the Battlefield.

I like Yoshi's more because it's easier to recover, but they are fairly close.

It's also easy to get tippers on FD, ToS, Smashville, Dreamland, PS3...and every other stage in the game.

It's easier on those stages because you can get them on reaction from tech chases.

I'm probably just terrible at this game.
But how are you meant to deal with his aerials, it doesn't seem to matter what I do, I get caught with one everytime.
Not only that, but I feel like I can't play aggressive with Marth after hes in the air, so he either catches you with Dair or he gets a free landing. So annoying :[

Who do you main Derk?