Catalyzer vs. Pulsar
Which would you choose and why?
you can use any variant of both.

I would use Polaris which is the elemental 5* of Pulsar. Because I normally use guns on enemies that I don't want to get too close to (Gun Puppies, Lumbers, Retrodes, Zombies and Phantoms) and they are all weak to elemental damage, I choose Polaris. I also find the shock very useful.
Next will be Biohazard because poison weakens enemies and stop them from regenerating health.
Then it will be either Supernova and Neutralizer depending on what you like most (blowing up enemies randomly or blowing them up when you want them to blow up).
I'm a gunner so I use Biohazard. Of course I'll get polaris too but Biohazard is the important one.
I decided on the Toxc Catalyzer line, but mostly because Ialready had an elemental gun (Voltech Alchemer MkII). I look forward to using it versus Slimes!
From the Catalyzer side I've choosen the non-poison side, I currently have Industrial Catalyzer
I didn't choose toxic, but I'm sure that toxic would be better than normal damage
From the Pulsar side, I've choosen to stick with Killowatt pulsar, even though I should have stuck with voltech alchmer mk11...
I need killowatt to complete my two remaining needed status affects that I can inflict on monsters. (Shock and Curse)