Honestly, both are good. I guess like with a lot of things it depends on context, as you say Pea Shooter rocks against defenders relying on armor. So yeah, Heavy Metal, Resonant, Armed Forces and whoever else I forgot/don't know.
Her SA2 is good for that. And her first is a mere damage booster (not to say 35% is low), BUT only to projectiles.
Inkling on the other side gets 25% bonus, even if only to herself, but that's for each living bro. 50% bonus is insane, though it also means she goes better as a lead to abuse all that power. Now, the funny thing about Inkling; her second SA. 25% is not small but is not big either.
(if I recall correctly) IT'D BE A SHAME IF BANG BANG BANG SHOT THREE PROJECTILES, EACH OF IT WHICH COUNTS INDIVIDUALLY!
Unless I'm screwing my math, that's 57%, almost 58% of it being unblockable. Now to make it better that's a special move, which you can equip more than once, which means you get to have that multiple times, which also plays off Peacock's marquee with a chance to immediately reset the cooldown of a special on use. You think this is absurd? Well haha what if I told you Bang Bang Bang also has Crit Rate on it, as if you weren't hurting enough? I am not wholeheartedly sure on this, but it may reach 100% if you lvl the move.
Thus, I have learnt to fear not the day Inkling puts out a legion of Georges' out for my head—but the day George puts out a gun-
Sorry I lost myself in the drama. So yeah, depends. Pea Shooter? Individually better imo, since her SA1 does work on herself and doesn't need teammates unlike Inkling, and her SA2 makes her effective at wearing down some great defenders. Quick math (which means probably-wrong math) tells me between her SA1 and 2 is somewhat a shift between 35% - 55% more damage (+20% from armor break, which has a 38% chance to apply from a 3-shot bang).
Inkling needs teammates to be truly frightening, but even only with one her SA2 is just ridiculous considering Bang (mind you, isn't it hilarious her card pose is exactly that?).
I'd argue that given the probabilities, even though her damage is lower, Inkling can outdamage Pea over time, since the armor break is six seconds, while Inkling, well, she just shoots you forever the three minutes and that bonus damage applies to everything, not just shots, so to Bandwagon, Good Fellows and all these non-projectiles hits on her combo attacks. This applies to non-armor guys, of course, it doesn't matter if your attacks go through when the fricking Heavy Metal is running on steroids because 5 stacks of armor.