Usually i5's have 4 cores / 4 threads. Although some of the first gen. i5's were 2 cores with hyperthreading. But usuaully the i5's win with 2 more cores over a dual core. Did you have any specific dual core in mind?
There are dual core i5 CPUs and quad core i5 CPUs.
Dual core i5 CPUs have a "u" in the model number like the i5-7200u. It has Hyper Threading (HT)which means it can act like a quad core CPU, but it is not a real quad core CPU. Programs needs to be designed to make use of HT otherwise HT does not really help performance.
Quad core i5 CPUs have a "HQ" in the model number like the i5-7300HQ. It does not have HT and it is more powerful than a dual core i5 CPU. But the program must be designed to use more than 2 cores for the quad core i5 to have better performance than the dual core i5 CPU.
The Sims 4 is a game that only uses two cores and it does not use HT. That basically means comparing two laptops with the same graphics chip, but one has the i5-7200u and the other has the i5-7300HQ, the performance of the Sims 4 will be basically the same on both laptops.