With those processor specs, assuming they are from similar processor generations, the 15" will smoke the 13" in anything that uses more than one thread as well as anytime youa re running more than one program. Unfortunately i7 alone doesn't tell you taht much - youw ould actually need the model numbers of the processor. For example a 7th generation dual core i7 would beat say a 2nd generation quad core i7 of similar processor speed. But in general, assuming the two computers are within a model year or two, the quad core one will be faster.