Let's see, the sploosh and the aerospray.
Let's start off with the positives. The sploosh and the aerospray have excellent rates of fire and they're both amazing at turfing ground. They both have pretty good mobility as well. With the sploosh being in the light weight class. The sploosh excels at point blank combat, having amazing DPS up close, and it's only a 3 shot kill. The aerospray isn't as good up close, but it has a bit more range, and two kits that allow it to cover loads of ground.
And that's about all the positive things I can say about both. Their weaknesses (short range and shot deviation) really limit them from doing much work. If anything, they're going to spend a lot of time turfing up the map, and charging up their specials. They can go for flanks, but a lot of weapons can simply walk back / zone them out so they can't fight them safely.
They're both pretty easy weapons to understand, and they can turf up the map quickly, which is appreciated in all skill levels.
But metagame wise, the aerospray RG became meta for a month, since baller was incredibly good, and the aerospray had the fastest baller in the game. And since then, the aerospray hasn't seen much since then. As for the sploosh, this thing has never seen much competitive use. The awful range and spread really limit how this weapon can attack players.
The Sploosh is the meta in both Turf and Ranked. Then again, it's pretty overpowered. Also kind of a crutch, which is why I tend to discriminate those who main it.
Sploosh is far from OP. The range barely extends out of the barrel, and the one kit that gets used (curling bomb / splashdown) is incredibly predictable. Plus, splat roller wears that kit better. Also, have you seen the dapple dualies compared to the sploosh? More range, DPS, and dodge rolls. Plus two kits that can play a great support role, and you have a sploosh on steroids. It takes the sploosh's strengths and dials them up, while giving it the option to play a hardcore support. Which makes the dapples much less predictable and linear than a sploosh.
The only disadvantage the dapples have in comparison to the sploosh is that neither kit has a bomb, and curling bomb is a nice sub for mobility. And that's about it. Sploosh just can't compete while the dapples are a thing. Even if it wants to play it's slayer / flanker role, it's going to be outclassed in 1v1 scenarios thanks to dodge rolls, and experienced players can deal with a sploosh trying to rush in and splashdown, as it's rather predictable.