I wouldn't counter SV, it has it's ups and downs for both characters. It isn't bad but you can do better.
Technically, Lylat is probably the best but I just really don't like it. BF has always worked for me.
Allow me to elaborate on why Castle Siege is a great choice here.
Phase 1: Awesome for Marth, platforms are positioned exceptionally well. Pretty much all of your platform abusing options are viable here. If you control the left side of the stage, Falco can't touch you. As long as you don't concede that side of the stage for long, you should be able to successfully limit his options and take care of business.
Phase 2: The abundance of high platforms and projectile interferences make this a nightmare for a campy Falco. Just use the obstacles to your advantage and try to keep him cornered. Expect a lot of phantasm, they will use it to escape the edges of the walkoff.
Phase 3: Basically a platformless Lylat. The ledges are worse for him then they are for you. The slanting slope also makes it tougher for him to camp you out with lasers. This is basically good for every reason that makes lylat good, except that there are no platforms here.
CP Castle Siege
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