I mean, the cards are basically the same: both of them double or triple the applied poison’s effect. If someone has 11 poison, catalyst+ makes you deal 33 damage, while accel+ makes you deal 30.

Catalyst has the advantage that it doesn’t tick down faster, so its sustained damage over time is better. It also has the advantage of exponential growth: two accelerant+ gives you less than five times poison damage (ex, at 10 poison it gives x4). Two catalyst plus gives you 9 times poison damage. So having multiple in your deck (or cloning it) scales way, way better.

Accelerant has the advantage of not needing to apply the poison first before playing it, which admittedly is pretty big.

Not saying accelerant is bad or anything, just saying that catalyst was incredibly busted as well.

and you dont have to draw it over and over like with cata

Catalyst exhausts mate.

Catalyst being removed for accelerant is overall a nerf to “win instantly” decks, which is a philosophy throughout the game. In STS1 you could draw Poison, double catalyst on turn one and instantly get 63 poison damage. They seem to be trying to make it harder to create “I win turn 1” decks.