That's not how servers work...
You’re right, my bad, instead the data from one console has to go clear to another part of the country, before heading to the other console and then heading back through that server to your console.
So a better analogy would be which is faster, direct route aka p2p, or route where you first have to take a detour far away from your intended destination, aka server.
No matter how you slice it, p2p is gonna be faster and better for a game like smash.
Servers work better when you have massive amounts of players such as mmos, so that there’s no need for a “host” player who could potentially drop out and force everyone off.
But for a fighter like smash? Directly connecting to your opponent and cutting out the middleman (server) is the only rational solution.
Fact is, no server is gonna “magically” speed up you or your opponents internet speed. If one of you has a crap service, it’ll still effect things if it runs through a server, and likely be worse as the server has to wait for each players system before updating what should be happening on the other players.
At the end of the day the only real solution Nintendo has left would to be booting players who don’t have good connections. MAYBE they could create better code, but I don’t see that helping much.