During Act 3 of Baldur's Gate 3, you will encounter a quest in which you'll have to decide if you'll side with a certain faction. In this guide, I'll discuss the repercussions of siding with either Stone Lord or Nine Fingers.
Baldur's Gate 3: Should you choose Stone Lord or the Nine Fingers Thieves Guild?
During the Aid the Underduke quest, you'll have to choose if you want to aid Nine Fingers Thieves Guild or Stone Lord. Morally speaking, there are no "best" options here, but if you want to gain a powerful companion, I'd say you should side with the Stone Lord.
Siding with Nine Fingers Thieves Guild means you'll have to kill the Stone Lord; however, there are a few consequences if you decide to side with the guild.
On the other hand, siding with the Stone Lord or Minsc means you're essentially helping a new criminal guild take over the existing one. For better or for worse, there are no options to help neither unless you decide to ignore the quest completely.
Siding with Nine Fingers Thieves Guild
Aiding the Nine Fingers Thieves Guild has a lot of repercussions; the most notable consequence is you'll lose Jaheira, a very powerful companion, for the rest of your playthrough.
Apart from losing one companion, you also will lose the chance to recruit Minsc, the Stone Lord. He is a very powerful melee ranger who can help dish out a ton of damage. If you're going to push through the narrative of helping an established criminal guild bleed the city's resources, you should side with the Nine Fingers Thieves Guild.
Siding with Stone Lord
If you're looking for arguably the "best" outcome in this scenario, I highly recommend you go with saving Stone Lord during the sewers level, as you'll be able to recruit Minsc and keep Jaheira before the end game.
You will also be able to recruit the Guild later on in the game, so don't worry too much about this decision. You'll help criminals either way, so there's no point in debating the morality of your decision during this quest; it all comes down to maximizing your opportunities to recruit all companions.
For more guides in Baldur's Gate, check out Baldur’s Gate 3: Should you let Astarion Drink Your Blood? in Pro Game Guides.