I'm planning on buying one of the two but I want to know which is better.
Pulsar Vs. Cataclyzer
I'd say to go for the Pulsar, since you can upgrade it into an elemental gun, which is great for gunpuppies and other enemies that you don't want to be in close contact with. If you're a swordsman, then the Polaris is one of the best sidearms you can have. The Catalyzer's only non-normal upgrade is Biohazard, which is fun to play with, but hard to make effective due to its slow bullet speed and much smaller hitbox when compared to the Pulsar.
I'd go with the catalyzer cus' I'm an outtie XD
Both are excellent and suck in their own ways.
Catalyzer:
Good- you can transform any enemy into a mobile bomb (combine with vortex for best results), bullets are slow but travel the farthest (good for switch mazes), and th explosions are really fun to setup. The damage is excellent too.
Bad- Some situations prevent charging up the gun, almost useless in PvP, slow bullets can barely hit wolvers in tiers 2 & 3, and the gun's mechanics are solely based on charging it.
Pulsar:
Good- excellent crowd control, explosions can knock back any enemy, even Trojans; Explosions hit Vana no matter what, sometimes cancels gun puppy attacks
Bad- very anti-social gun; annoys swordies, bombers, and gunners alike (mainly swordies); charge attack sucks, you have to be decently far away to use the crowd control aspect of the gun, explosions can block out enemies, which could be charging attacks.
I recommend pulsar, because it is an excellent sidearm, despite being the most annoying gun to play with.
Note to swordies: If you see someone using a pulsar gun, leave them in their corner and attack a different mob of enemies.
It's easier to use the pulsar and really useful for swordsmen
Catalyzer is trickier to use.