Is it possible to tell who is who in each scene?

I would like to add some more points and try to point which was the Borden who loved Olivia and the Borden who loved Sarah in each scene.

1) I loved Sarah. He loved Olivia. says a lot of things in the last scene of the movie. BORDEN WHO LOVED SARAH loved Sarah and BORDEN WHO LOVED OLIVIA loved Olivia. Now how can we say that the living one is BORDEN WHO LOVED SARAH? Before Fallon i.e. his twin brother joined him in the movie, he fell in love for her and he said "I loved Sarah"

2) BORDEN WHO LOVED SARAH is the Borden who took interest in Sarah and went to her house.

3) Remember when Borden who loved Olivia gifted her the key, the conversation was like:

I asked you last week
You caught me in a wrong mood
But you wont ever
Sarah..
I am gonna have to change my mind, aren't I? 

So it is presumable that when she requested for it, it was BORDEN WHO LOVED OLIVIA, who was in the wrong mood. But as soon as he told BORDEN WHO LOVED SARAH, he took no time in arranging a house.

4) In the party after Borden was compelled to give the keyword "TESLA" to Angier, he was acting very bad to Sarah, this was probably BORDEN WHO LOVED OLIVIA and Fallown was there BORDEN WHO LOVED SARAH because When Sarah requested him to escort Olivia to home, despite Borden who loved Oliviard said Don't ruin this evening he stood up and took Olivia home. After that Borden who loved Oliviar quarreled with Sarah, which proves my opinion. At the end, Sarah said:

No Alfred stop. This isn't you. Stop performing.

5) Olivia came to BORDEN WHO LOVED OLIVIA, with whom she fell in affair with.

6) When Borden who loved Sarah was going to take them for the zoo, he said to Sarah

I love you. I will always love you.

and Sarah said: You mean it today.
This is BORDEN WHO LOVED SARAH in action.

7) In a scene where Borden was talking to Fallon, he said:

And, uh... Sarah,Uh, at least she knows
that something is not right,
Talk to her, just
convince her that I do love her.

Here BORDEN WHO LOVED SARAH is talking to BORDEN WHO LOVED OLIVIA. We get the proof in the next scene, when he meets Olivia and she kisses her and he said:

It's nothing. It's just that

sometimes it seems wrong.

8) Before committing suicide in the last fight, Sarah was talking to BORDEN WHO LOVED OLIVIA and Fallon was the BORDEN WHO LOVED SARAH who took their daughter aside. That is why, When Sarah asked "Do you love me?" He said No, not today

9) In the last meeting with Olivia, he said he loved her and he did not mention Sarah's name once. that is the BORDEN WHO LOVED OLIVIA. Olivia was upset with the fact and said It is inhuman to be such cold.

10) And the Borden who loved Sarah lived and who was hanged was BORDEN WHO LOVED OLIVIA, who said I am sorry for a lot of things. I am sorry about Sarah. Did not mean to hurt her. You two live for both of you.

That means the living one was BORDEN WHO LOVED SARAH and the hanged one was BORDEN WHO LOVED OLIVIA.

11) In the opening scene when Sarah informed about her pregnancy to Borden, it was who loved Olivia, that is why he said:

We should tell Fallon

So these are some other points where we can differentiate between them.

In some scenes : Yes.

The only way we can differentiate these two people is by who they loved. One of them loved Sarah and the other Olivia.

• At the scene where Sarah tells Borden (the one who appears on the scene) that she is pregnant his immediate reaction is : "We should tell Fallon". In this particular scene Fallon is the Borden who loved Sarah.

• All the scenes where Borden tells Sarah I Love You, but she reacts saying "Some days its not true.". Example. In all of these scenes she is actually talking to the Borden who loves Olivia.

• The scene where Borden talks with Olivia asking her to believe that he loves her. Its obvious that the Borden here loves Olivia.

• The scene where Borden and Sarah have confrontation and we see Fallon taking their child outside. Here Sarah is probably arguing with the wrong Borden (i.e the one who loves Olivia) and Fallon in this scene is the Borden who loved Sarah.

• At the Bullet Catch Trick scene when Angier points gun at one of the twins performing the trick, he is supposedly asking the wrong twin, which means the Borden whose fingers were cut by the bullet is the one who loves Sarah. Because if you see the scene here, its clear that this Borden has cut his fingers fresh (with the help of other Borden) and he isn't bothered much about the child waking up and he just wants to get back to work, this implies that he is the Borden who loved Olivia. If the one who tied the knot is the Fallon at the scene of "Bullet catch" then it means the one who tied the knot at Julia drowning scene is the one who loved Olivia.

There could be many other scenes where we can figure out who is who, will update my answer as I think of more.

There is one way to differentiate between the two. If you look at his left eyebrow the style changes between the two. Fallon has a slight line cut out of the side of his eyebrow where as Borden's is just short. It is hard to notice but it is there.

SPOILERS ALERT!!

I would like to call them Sarah's Borden and Olivier's Borden. For me, SB is more gentle while OB is a little bit more aggressive.

In the scenes with their love ones (or even their twin's love ones) it's quite obvious to tell which borden was in the scene. Like when Sarah first told that she's having a baby; the reaction from Borden was "we should tell Fallon" which prove that he's not Sarah's husband. While the 2 Bordens kept saying that "Secret and tricks are their one LIFE" ..almost everything they said to the girls was the truth.

I don't think that Sarah knew that there were 2 Bordens. She fought her last fight against OB like she fought her own husband.

In the rivalry part, OB had more passion to conquer Angier. He shouted at Fallon (SB) to break down Angier's Transported man trick and he's the one who didn't let go which lead him back to the show again and be trapped.

BTW, this is my most favorite Nolan's film. And it's very fun to see Michael Caine called Christian Bale "Alfred" on screen. ^_^

I think one Borden is primarily the ingenieur, and the other is primarily the performer. In this way they have a similar relationship to Cutter and Angier.

There is a scene where Borden is yelling at Fallon, "Why can't you outthink him!?" I think this is Borden the Performer, who is obsessed with figuring out Angier's secret, taking out his frustration on Borden the Ingenieur. Subsequently the Performer notices the blind stagehands removing Angier's water tanks each night, and he informs the Ingenieur, who then goes to investigate for himself. But upon returning says that he still cannot figure it out, and tells the other Borden to drop it and leave Angier alone.

So the Ingenieur is not obsessed with Angier the way the Performer is. I think this subtlety could be detected in other scenes.

Also, the Performer seems more prone to emotion-based behavior, while the Ingenieur is typically calm and reasonable. It's the Performer who is obsessed with competing against Angier, who treats Sarah poorly, and yells at Fallon. The Ingenieur is the one who appears first as Fallon, tries to convince his brother to leave Angier alone, and genuinely loves Sarah (who can sense the difference and in one scene actually tells the Performer to "stop performing!")

One of the Borden Twins has a scar above his left eye -- in the book it was on his hand from a woodworking accident because magicians tended to start out as apprentices to carpenters, to learn how to build deceptively small looking cabinets -- but when we see him wearing the fake beard do not count because he is wearing makeup... probably also to cover up the scar.

If you follow the scar it reveals that they DO continue to change places while in jail. That was the purpose of the scene where he distracts the guard and chains him to the table: it shows that he's in control and could escape at any time if he wanted to.

I also notice the way that they speak is slightly different. SB has a more plain spoken accent, OB is rougher, even a tiny bit cockney.

It is totally possible to tell the difference between Borden and Fallon. I was watching the movie today and noticed that Fallon has a small nick in his left eyebrow whereas Borden does not. At any point in the movie that has a reasonably close shot of the characters left side you can tell whether it is Borden or Fallon.