Travis stops at a convenience store to pick up a few things and ends up killing a potential robber. The only difference in this scene from script to movie is that there is a little more dialogue in the script. Schrader tended to fill his scenes with that "hello, how are you" kind of dialogue that directors don't like. Scorsese took it all out.
Now Scorsese shows the American Bandstand scene. I wrote, "Travis frowns at the TV. Is he curious, mystified, angry, or all three?" Schrader answered that question. "…his face is hard and unmoving. He is, as the Scriptures would say, pondering all these things in his heart. Why is it the assholes get all the beautiful young chicks?" So I guess the answer is, "all three."
Schrader goes from the murder at the convenience store to Travis killing his TV. He also didn't describe Travis as caressing his gun as it was a cat or even his own penis. Scorsese stuck that little bit in. In Schrader's world, Travis tries to bring the TV back to life, but Scorsese went straight from killing it to holding his head in his hands (AND the gun) and muttering, "Damn, damn."
By this time Scorsese has shown Travis at TWO Palantine rallies. Schrader hasn't even done the first one.
Travis visits with the other cabbies. Schrader included more "hello, how are you" dialogue and this is the first time in his story that the others call Travis "Killer." In the movie he gets his nickname before he buys the guns. In the script it's not until after, which makes more sense. Travis tells Wizard he has to talk to him and Wizard completely misses the clues that Travis is cracking up. Scorsese moved this scene (with the late, great Peter Boyle) way up in the time-line, but Schrader put it here, during Travis' slow break with reality.
Now Schrader finally gets to the first Palantine rally, where Travis talks to the Secret Service agent and gives a false name and address. The only real difference is that Scorsese (or DeNiro?) put in the little bit about too many numbers in the zip code. Nobody realized DeNiro is as deft a comedic actor as he is with drama until years later, but he always had that sense of humor. Anybody who has seen Greetings and Hi Mom knew it. So he could have been the one who came up with the extra numbers.
The other difference is that Schrader adds a diary entry about how many more rallies are coming up. In his story, Travis is already planning his attack, but I got the feeling during this first rally that Travis was still trying to make some kind of human connection. It's the placement of this scene in the time line that makes the difference, as well as that diary entry. By showing it to us right after Travis starts to get into shape, Scorsese tells us that Travis is in the middle of a life change. In Schrader's mind, he's already made the change.
Travis nearly hits Iris and her friend and follows them until they pick up a couple of johns. Schrader put in another child hooker who hits on Travis while he watches Iris and her friend. "TRAVIS quickly turns his face away from her in a combination of shock, embarrassment and revulsion. He is the child caught with his hand in the cookie jar. The very presence of this crassly, openly sexual human being frightens and sickens him."
Scorsese decided he didn't need to drive the point home so hard. Travis is obviously not attracted to Iris and the other child hookers, but he's also afraid to approach Iris.
Scorsese also put this second "meeting" with Iris earlier in the story, before the first Palantine rally, the "you talkin' to me?" scene, and killing the potential robber.
In Schrader's world, Travis has already killed his TV. In Scorsese's world, it has yet to happen. So now we come to the second Palantine rally, where Travis sits in his cab and watches while we hear what he's written to his parents about his work in the government (Schrader says it's the Army) and the wonderful girl he is seeing (who dumped him months ago) and how he wishes he could call more. In the background, Palantine gives a speech about putting an end to disunity and working together. A policeman tells Travis to move it along.
Scorsese inserted the scene where Travis kills his TV here, but Schrader went straight from this to Travis finally going to see Iris. In the movie, he does this here too, but first he kills his TV.
Travis goes to see Iris, who sends him to Sport. Schrader put in the bit about Sport calling him a cop to make sure he isn't, and Scorsese added an exchange about how Travis could do anything he wanted to Iris, come in her mouth, fuck her up the ass, etc. Travis is disgusted, but pays for the time.
Finger-man is "OLD MAN" in the script and Timekeeper in the movie. He takes Travis' .38 in the script, but Scorsese doesn't mention or show any guns in this scene.
In the script, Iris gets more undressed and does more to Travis. Obviously Scorsese couldn't shoot it that way because Foster was only 12 at the time, but Iris still unnerves Travis. Schrader didn't have him throw her away from him to the couch. In the script he's gentler, and more uncertain. Other than that Scorsese didn't change the scene at all. All the dialogue is almost exactly the same.
The following scene, where Travis gives back the $20 bill, is the same too, except the old man gives back the gun.
At this point Schrader inserted a scene with Palantine that Scorsese didn't use at all. He went straight to breakfast with Iris. This scene is almost the same. Iris has a little more rambling dialogue that Scorsese cut and she also tells Travis, "You're not much with girls, are you?" Scorsese probably thought that line was a little too expository. Travis also talks about killing people in the script, which he doesn't in the movie.
There's some dialogue in this scene in the movie that refers back to the first scene with Sport. Travis tells Iris how Sport talked about her little pussy and fucking her in the ass. Schrader didn't include this because he didn't have in the first scene.
Schrader went from the Palantine scene to Travis watching the hotel, which Scorsese cut, but he did include a scene of Travis watching the building where Iris works.
Inside, Iris tells Sport that she doesn’t want to do this any more. Sport holds her tight and gives her the speech about wishing every man could have her love how he's so lucky. Schrader made this scene more sexual, but Scorsese kept it pretty innocent, except for the dialogue, which was creepy.