There are 4 parts :

Resident Evil 2 (1998) scenario differences: Leon vs Claire, Scenario A vs B, and specific A/B differences for each character.

Part 1: Basic Difference Between Leon and Claire

Leon Scott Kennedy's path includes Ada Wong as a supporter and Ben Bertolucci as a related character. He does not need to find the Bomb & Detonator to open the Chief's room and finds the Heart Key at Marvin's place. To unlock the sewer passage, Leon must find four Plugs. He explores the left area of the basement (Parking Lot) and the northeast sewer area. When seeking the Club Key, Ada gets ammo for Leon where Sherry began. Leon first meets Annette at Sewer 1 and does not need to find the Lighter.

Claire Redfield's path includes Sherry Birkin as a supporter and Brian Irons as a related character. She must find the Bomb & Detonator to open the Chief's room and finds the Heart Key at Chief Irons' place. To unlock the sewer passage, Claire must find three stones. She explores the right area of the basement and the southeast sewer area. When seeking the Club Key, Sherry gets ammo for Claire where Ada began. Claire first meets Annette at Sewer 2 and does not need to find the Small Key.

Part 2: General Basic Difference Between Scenario A & B

Scenario A features G-Infant, William 2, William 4, and the Alligator as big bosses. The character cannot explore all the places the B scenario character can. Zombies destroy windows and dart in when the character returns to the Library a second time. The scenario begins from the street to the front gate of the Police Station. The Valve Handle is in the back courtyard. The Blue Card Key is obtained from Marvin. The Unicorn Medal is hidden under Chris's diary. The Lighter is in the Waiting Room. The Diamond Key is in the Antique Room. There is a cord. The Crank is in the File Room. The Machine Gun is only in the Weapon Storage. The character cannot enter the laboratory elevator or the Licker experiment room. The character does not need to find the Power Room Key and Master Key.

Scenario B features William 1, William 3, William 5, and Mr.X as big bosses. The character can explore entire places the A scenario character has gone. Zombies destroy the windows and dart in when the character first goes to the Library. The scenario begins from the street to the back gate of the Police Station. The Valve Handle is in the east office. The Blue Card Key is in the Antique Room. The Unicorn Medal is on the wall of the 2F main hall. The Lighter is in the File Room. The Diamond Key is in a different position. There is no cord. The Crank is in different positions. Machine Guns are in the Weapon Storage and Licker experiment room. The character can enter the Laboratory elevator and the Licker Experiment room (depending on the A character). The character does not need to find the MO disk or Vaccine, meaning the Lab Card Key is an unnecessary item.

Part 3: Difference Between Leon A & Claire A

In Leon Scenario A, you get the Wolf Medal from the corpse. Your next meeting with Annette is at the West area of Laboratory B4. You do not have to make the G-Vaccine.

In Claire Scenario A, you get the Wolf Medal from Sherry. Your next meeting with Annette is at the door of William's experiment room, Laboratory B5. You have to make the G-Vaccine.

Part 4: Difference Between Leon B & Claire B

In Leon Scenario B, you grab the Diamond Key from Sherry. When seeking the Club Key, Ada gets the pendant from Sherry. You grab the Crank in Sherry's first place. Your second meeting with Annette is at the Laboratory elevator. You get the Master Key from Ada.

In Claire Scenario B, you grab the Diamond Key in the S.T.A.R.S. Office. Sherry does not drop the pendant. You grab the Crank in the dog's cage area. Your second meeting with Annette is at the Monitor Room, Laboratory B5. You get the Master Key from Annette.