Chapter VI will not provide many differences in gameplay for both brothers. The only difference will happen when you will try to enter an estate during one side mission.
After reaching Ramos' mansion, go towards the water tower. When you will move close to it, use the lasso to go onto higher level.
The second difference is the way in which you will enter Ramos' house. Playing as Thomas take the outside stairs and use once again the lasso in order to reach another balcony. You will find there an open door.
Playing as Ray the difference will be also connected only with entering Ramos' estate and his house.
Being next to the main gate in Ramos' estate set a dynamite in marked spot and watch like the gate is blowing up (remember to move back in order not to die).
An enter to his house is even easier, just brake down the door under the stairs.