I figured this would get into a "which choice is better" debate eventually. To me, tactics-wise it's a no-brainer. Whether or not the Ben-Hassrath should have had the foresight to avoid all possible negative outcomes or whatever on the Storm Coast, their aid is far more vital than one single mercenary company. Yes, they're not trustworthy (outside of fighting Corypheus), which is why they're kept at arms-reach when aiding the Inquisition, but their help would be undeniably instrumental in stopping a threat that could consume the world (meta-gaming it of course doesn't matter but whatever). Throughout history major powers have united against common enemies many times despite not trusting each other.
Remember what Iron Bull says when first discussing needing an Inquisitor? "We choose those who can make the hard decisions, and live with the consequences." And as Inquisitor you should be able to make the hard decisions.
...Now... that doesn't mean I always sacrificed the Chargers. When role-playing characters who hated the qun, they let their biases cause them to make a military blunder by saving the Chargers. And after Trespasser that choice is far easier to make. After all, we see what happens to Iron Bull after losing his family. We don't ever see those 100 dead qunari on the dreadnought or those left on Pal-Vollen grieving for them. And we also see that the qunari attack the south two years later regardless of what you do while the Chargers remain loyal. That makes allying with the qunari knowing what's coming harder. It's all emotions and meta-gaming influencing your choices.
Side-note: Speaking of qunari being untrustworthy, in Trespasser it once again shows Leliana's incompetence as a spymaster for just dismissing Iron Bull of not knowing anything about the qunari because he said so. I figured he either was kept in the dark for fear Leliana was actually thorough enough to interrogate him, or he was lying. It turned out to be the latter. Hell, his name is "liar."
Leliana isn't incompetent. She's working for a more powerful employer.
The visions, the entire DLC focused on her, the fact that the titans (or whoever is ultimately behind lyrium's song) think she's important enough to raise from the dead. She's almost certainly a double agent. Possibly an unknowing one, but a double agent nonetheless.
If killed-in-Origins-Leliana had been raised by a faith spirit, I'd say it was just luck she came back. But lyrium's song raised her, and
gave her a job to do.
What could that job be, but influencing the inquisition? And what better way to influence an organization than by planting its spymaster, the person who vets everyone else? Who's in charge of screening
her? Who checks whether she's intentionally skipping over people? No one.
She says "I must have missed X, Y, and Z shifty-looking people", and we believe her. We look at this Orlesian bard who grew up soaked in the Game, and we totally buy it.
Yes, you must have made a mistake, silly you!
Oh, another mistake, how clumsy!
Our entire organization is riddled with Ben-Hassrath and agents of Fen'Harel? Pish-tosh, these things happen from time to time.
Ah, I see you turned into a flock of birds and flew away, saying your work here is done? My, my, how quirky and adorable and completely unsuspicious!