My picks were Piranha Pit, and the blessed map called Mahi-Mahi Resort.
Piranha Pit's gimmick with the ramps are great, even if they are semi-avoidable. The middle ramps are great for flanks onto your opponent's plat, if your close ranged, and the ramps are excellent peaking tools for snipers. Zones on this map is absolute heaven, Tower Control on this map is alright. Rainmaker was a mess, so it got removed from online play. Honestly they should have patched it so that the rainmaker pedestals are somewhere else, but the map really didn't support rainmaker in the first place. The biggest problem with Piranha Pit though are the two big pits at the west and east ends of the map, they're so worthless outside of turf war and rainmaker (removed). Still, great map with just some design flaws.
Mahi-Mahi Resort, where do I start with this great map.
First of all, it looks Amazing with all the COLORS!!!
Not only is this masterpiece of a map aesthetically pleasing, it's also rather balanced for all weapon types.
For snipers (like myself) there are LOADS of perches, shot angles to choose from, from the raised platforms in mid, to the back street useful for getting shots in.
For close range weapons there's great cover distributed throughout the map, so that long-range weapons don't dominate, and great flanking routes through their sneaky, through the wall close to snipe, and their islands help you flank successfully.
For sloshers and blasters, trust me there are tons of great angles for you guys to get splats on the unsuspecting charger or splatling.
The stage also changes halfway throughout the match, I forgot what it was for other modes, however I love the water rising, because it makes player adapt to the map. Which is what splatoon should really be about: adapting to things that are new, and then seeing how that affects the meta.
But that's just my opinion. :/