(Ranked for Turf War only, since I got tired of Ranked pretty quickly)
1) Kelp Dome: Love the layout, loads of space to cover means high scores, the walkway leading to the central area has a strong risk-reward element and while the central area is keenly contested, battles usually move quite easily into opposition territory as well. Very nicely rounded.
2) Arowana Mall: The central choke-point is compact and fiercely contested, but intelligent play allows for thrilling dashes across it into enemy space. A secretly strong strategic map where it's easy to find action and enemy ink quickly.
3) Saltspray Rig: Easily the best of the 'limited space' maps, it's complex enough that you have to keep an eye on multiple areas if you want to win, particularly the blocks of space at the top and bottom. Nicely designed and often exciting, but a little too easy for a team with the right mix of weapons to dominate.
4) Blackbelly Skatepark: The weakest of the wide open maps is also an easy one for high scores, but simply not all that interesting to navigate. There are so many places to incur into enemy territory that it loses some of its excitement, and there's not much advantage to gaining the central area (unless through beacons, which become amazing).
5) Port Mackerel: Solid tactical map, darting in and out between the crates encourages fast-reactions and making it all the way to the enemy base is a stupendous feeling, particularly if you manage to take the elevated flanks. The grid-like structure means the team with the most long-range weapons (unless only chargers) should win, though, and the inability to climb up almost anything is frustrating.
6) Urchin Underpass: A solid mix of everything, with a central area that is tough but rewarding to dominate and enemy territory with just enough entrances to be exciting but not impossible to breach. Downside is that it's just not all that exciting, and rarely gets scores as high as the Skatepark either.
7) Walleye Warehouse: Too narrow. Yes, it's frantic, but the Killer Wail becomes insanely overpowered when well placed, the lack of width means a stronger team can dominate easily, and while battling can be exciting, it's not really what Splatoon is about.
8) Bluefin Depot: Urgh. Barely any space to paint, a huge chunk of enemy territory that is inaccessible without airstrikes or being forced to walk, two central areas that in theory should invite some interesting tactics, but in practice devolve into prolonged skirmishes and are annoying to get down to. More a battle arena than a turf war, and not much fun to play.