AR grenadier shootout

In terms of skill, I'd say Zas. Her debuff makes it useful even vs bosses.
But also consider FAL's salvo if you want to clear maps efficiently if you're corpse dragging.

GLHF ^^

Zas' skill is good since it contributes to her own damage or overall team damage with a debuff, but the grenade itself is rather weak with it's 3x multiplier. She doesn't fulfill the same role as other grenadiers in that regard, unless your enemies are swarms of dinergates. Which leads to her use as corpse drag machine in 6-3N, where that grenade is just enough.

I think it depends from situation to situation but if I had to guess for general use, I would say FAL's is the best. First of all, it is much more efficient than 416s because 416s will Overkill much of the time which is wasting potential on most units. FAL's, in contrast, is the same damage divided into 3 grenades that do 5x damage a piece instead of 416s 15x. What this means is you can buff the heck out of FAL's damage and her grenads will not Overkill and they will distribute damage very efficiently while still hitting hard. Also FAL's has a 2 second shorter initial cooldown of 6 seconds. Zas' skill is harder for me to analyze because it is pretty complex but it would work wonders on tanky frontliners and bosses and it is also impossible for it to Overkill in most situations. Plus it has a fail safe that raises her damage by 60% for a hefty 8 seconds. Finally, Zas' skill only has a tiny initial cooldown of 4 seconds. So Zas and FAL have the better abilities and I think they're pretty evenly matched. They are both great for hitting multiple and single targets but they work differently so it's hard to predict which one will perform better. Also you have to consider that FAL's base damage is HUGE at 57 so her grenades will hit extra hard. I do want to add that HK 416 may have the worst ability but she has other things going for her like custom equipment she can get. EDIT: On the other hand, Zas' grenade has a huge radius that will be hitting at least half of all enemies on the screen most of the time but it has a smaller damage multiplier. Sorry for how long this is but I like to be detailed.