I think the is the Ink/Octobrush's best stage
YES
It's a great stage for the Octobrush, and I could see Inkbrushes thriving here as well, and here's why:
1) So many corners! There are quite a few spots just outside the center (or those areas to the left/right of it) where you can lie in wait behind a wall for enemies to come by so you can splat them. It's worked pretty well for me.
1x) Also, an Octobrush-specific thing that's probably useless outside of Splat Zones: Drop a Squid Beakon on the grating above the other team's Zone, then jump there every time you get splatted. I've only seen it get destroyed by the other team once or twice, and I've always gotten at least one free superjump back to their Splat Zone so I could re-cover it easily. Dunno if that works beyond B+-level lobbies that I'm always in, but it works really well for me most of the time.
2) Chargers are surprisingly easy to beat here. You can easily reach them in most of their spots (the center tower can be inked up from the platforms, the halfpipes can be run up to, the walls by the halfpipes can be run up to; really, the only difficult one is the area on the side (past the halfpipe), and that can be reached as well), so you can generally at least reach them, if not actually splat them.
3) Beyond the spawn point area with all the slopes, you can pretty much run anywhere at super speed, only occasionally squidding up a wall or halfpipe. I recommend taking the left path to the enemy spawn, since you might surprise a Charger getting set up there and if not you can ink up their spawn area, which is annoying and generally has to be cleaned up.
Though as for best stage, I think Walleye and Triggerfish (though that could be Octo-only) and
maybe Mackerel (not sure on that one) might give it some competition.