superblobby

The difference in killing Darko is pretty much nothing. Like, basically just the line of conversation between you and Roman on the way home. You kill him, he'll be like 'I guess you did what had to be done' if you let him live he'll be like 'You're letting go, that's a good thing'.

However, the difference between taking revenge, and taking the money, changes the entire storyline for the rest of the game.

Taking revenge:You go kill Dimitri, woop. Kate accompanies you to Roman's wedding, and is accidently shot by Peggorino, who was aiming at you, for being a traitor much.

If you take the money, Dimitri stabs you in the back again, you take the money, Kate isn't happy with you taking the money, so doesn't come to the wedding. Roman gets shot instead, but this way you'll be $250,000 richer.

No new safehouses that I know of.

Alexzander

If you take revenge Kate dies, and if you make the deal Roman dies so it's your choice who will die.