Does taking revenge instead of the deal in GTA IV affect the ending?

Solution 1:

A lot of the information below is from the Wiki in addition to when I experienced this game.

This is a pivotal point in the game. It's going to be difficult to explain this without spoiling it, so I'll use the spoiler markup as necessary. If you are after the money, either option will grant you $250,000 eventually in the progression of the missions.

If you take Revenge:

You will do a mission called "A Dish Served Cold". It warrants no cash reward but

You kill Rascalov, which sets the stones in place for the next mission.

After this mission, you will begin "Mr. and Mrs. Bellic." It warrants no cash reward, but

When Roman and Kate are leaving the church they got married in, a car speeds by, with Jimmy Pegorino firing a gun into the crowd attempting to kill Niko, but his shots miss, and he hits Kate instead, killing her.

The last mission in this series is called "Out of Commission." You will earn $250,000 after the mission. What happens is

You seek out Pegorino, and after some chasing, kill him.

If you take the Deal:

The first mission is called "If the Price is Right." Should you choose this path, you will receive a cash reward of $250,000 for this mission. What happens is

The deal is off, since Rascalov killed the people involved. Niko, unknowingly, is heading straight into a gunfight. You steal the money involved with the deal, and make an escape.

The next missions after this is "Mr. and Mrs. Bellic." This mission as you can see, takes place no matter what path you choose. However,

A man in the crowd walks up behind Niko and attempts to shoot him. Niko manages to wrestle the man with the gun and while doing so, a stray bullet is fired, which hits and kills Roman.

The last mission in this series is called "A Revenger's Tragedy." There is no cash reward, but

Niko hunts down Rascalov. A chase ensues, and eventually, Rascalov gets what was coming to him and is killed. In addition, after the mission, Niko receives a phone call from Mallorie, saying that she is pregnant with Roman's child.

It should be noted that whichever path you choose (taking the deal, or getting revenge) you start, you cannot go back. You'll have to make a choice.

Solution 2:

Yes, your choice will affect the ending. Specifically, it will affect the current mission, as well as the following 2 missions.

Since there are only 3 missions left (one of which is simply a cutscene), you might want to make a separate savegame so you can witness the results of both choices.

Deal

If you take the deal, Roman will be shot (and dies) during his wedding by an assassin sent by Dimitri Rascalov to kill Niko. In the final mission, you will have to chase and ultimately kill Dimitri.

Revenge

If you take revenge, Pegorino will attend Roman's wedding in a car and start shooting, killing Kate in the process. In the final mission, you will have to chase and ultimately kill Pegorino.

The reward money for either choice is ultimately the same. If you take the deal, you will receive $250 000 after the deal, but no reward for the last 2 missions. If you take Revenge, you will only receive your $250 000 reward after the final mission.

Also, while both endings are different, they are still fairly similar to one another.