For Eternatus, the poison from Garbodor won't help much. 4-0-1/4-0-2 Obstagoon line with a couple candies is going to help out the damage more as well as give you a couple free wins against basic-only decks. And you'll find that it's not easy to get 8 Pokémon on your bench turn two, nor do you need to in most cases.I rather use Garbodor as an option. It poisons the opponent as a bench-sitter. Expect on Turn 2, your bench is full at that state. Its very rare that their bench was full on turns 3,4, or even 5. Turn 2 270 dmg
As for Toxitricity, ideally Garbodor would be the bench sitter, but in reality it's not that easy to set up a stage one on the bench by turn 2 while also attaching an energy every turn. Garbodor will still be played in many Toxitricity lists, but a backup like this is very good.
If this has a 2 retreat cost so it works with air balloon, it's equally as good as Garbodor. It's not easy to setup a stage one right away every game while needing to attach every turn and not being able to play a supporter on turn one in half the games you play. This card can be grabbed whenever by a simple Quick Ball and can turn a switch into a Hypnotoxic Laser. I'd argue that it's significantly better than Garbodor.