If two cars travel at the same constant speed in a straight road say 1km, can one be faster than the other?

To give it more context, I was at a social gathering yesterday and afer some time the conversation deviated to cars. We were talking about fast cars and all that. Anyway someone was arguing that a 100mph in a Mercedes ML is not going to be equal to a Lexus LX570 or a Range Rover. I m not going to pretend that I... show more To give it more context, I was at a social gathering yesterday and afer some time the conversation deviated to cars. We were talking about fast cars and all that. Anyway someone was arguing that a 100mph in a Mercedes ML is not going to be equal to a Lexus LX570 or a Range Rover. I m not going to pretend that I have a clue about all the technical stuff, I'm ignorant to most of it, engine size, torque, horsepower and other factors just know how to drive them. Obviously, cars are divided into different classes, some are geared towards comfort, another luxury, etc
I did not put too much thought into it but my answer was the Porsche will probably reach 100mph faster than the others but if two cars are driving at the same constant speed (100mph) why would one be faster than the other?.
In Bad Boys, Will Smith stated that the Porsche he was driving could do 0 to 60 in 4 seconds, and I 've heard of other cars that do similar and even surpass that. If a Prius, Maserati and 911 turbo all are the same speed in a straight road, will one overtake the other or would they be equal? Or is it not that simple?
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