I save the Qunari every time. While it kills the Chargers and might not be the best for Bull, scuttling the alliance means the Venatori spy network continues and their plot to burn down half of Denerim succeeds. 6 guys versus an entire spy network and half of Denerim's population seems an easy choice. Though I wish there was an option for the Inquisitor and/or one ally to run to them and intercept the Venatori. I even had Dorian's focus haste ability and thought that would factor in.
Here' the thing.
1. You have no idea at the time what the Venatori are doing. So it's not a choice about Denerim.
2. You know the Chargers personally by this point.
3. Do you trust the Qunari after Cory is gone?
- For me the alliance wasn't as important to me than Bull and the Chargers. And even after the loss of Denerim, I wouldn't change my mind in a redo. However I do blame the Qunari for the loss of their ship and the Loss of Denerim.
Here's why, their intel was flawed on that beach, as such it was their fault the choice was made. As for Denerim they choose to withhold that intel which could have saved lives, hell if they were smart they would have saved Denerim and made sure everyone knew it.