I'd say the Rabid Snarbies. You need a Beast Bell to kill them, while you only need the two Red Roarmulus Twins to be looking in each other's vague direction to kill them.

Peoples, do not forget, that the Twins bullets is powerful enough to make the Snarbolaxes vulnerable!

Rabid Snarbies are monstrous creatures infected by the core's darkness whereas the Red Roarmies are the best weapons made by gremlins who've lingered near the Unknown passage for far too long so they're both pretty scary but there are a few reasons why the Snarbies are done for.

1. Poison < Fire+Shock
Poison does weaken and prevent healing but seeing as how the Red Twins don't heal, it'll make little difference; However, if the Rabid Snarby were on Fire and Shocked, they'd deal damage a lot more often than twins, seeing as how they only deal piercing damage against the twins who are constructs with such great armor that they can only be brought down by their own weapons (which I'm sure are more powerful than a bell that makes the Rabid Snarbies vulnerable.)

2. Habitat supports the Twins.
If the Twins popped up in the Snarby's field, they're be uninfected by the barbs and would proceed to shoot the bell, their rockets landing only on each other and the poor unfortunate Snarbies that they intruded upon.
If the Snarbies went exploring and stumbled across the Twin's room. Their primal brains would have them running face first into the rockets in attempts to bite the Twin's incredible armor. They'd not know how to handle the switch and would not be able to survive against the flurry of rockets cover the field.
If in a blank area, the twins would still overpower the Snarbies due to the Snarbie's lack of rocket evading skill and the Twin's lack of darns to give.

3. The Twins have more effective moves.
Snarbies and bight, burrow, and shoot spikes (as well as roar.) They're protected by the darkness of the woods but can be stunned by a mere bell.
The Twins can shoot rockets, flaming rockets, shock bursts, and mutha'huggin' LAZORS. Their armor is so tough that they first gotta hit each other with their own rockets to suffer any damage.
Have you ever tried biting a giant robot that shoots lasers? What's better, rockets or barbs? Snarbolax is a wolver on Steroids but the Red Roarmulous Twins were based off of a Rocket Puppy Tony Stark designed to beat Superman, Goku, and Chuck Norris while he drank his aftermorn tea (and by "tea" I mean "Whiskey")

Of course we all know that Dark Fire Vana can beat both the Snarbies and Twins after eating some Frozen Yogurt that was Ice Queen.

...Could've used a Recon Cloak.

And Tony Stark designed such a Rocket Puppy? Well, where was it when Loki was flyin' around with... wait! Not gonna spoil it.

Also, my thread is not stupid. It only pretends to be stupid while, the whole time, you are letting your guard down. It's biding its time... you have been warned, it is not as stupid as it seems.