• Cache sizes are also smaller on Core i3 processors (onboard memory). They have slower clock speeds and manage less RAM than other Core CPUs. The top clock speed of the ninth-generation Core i3 desktop CPUs is 4.6 GHz as of this writing; however, that is only for the higher-end Core i3-9350K.
• Although an i5 does not have Hyper-Threading, it does have more cores (now six instead of four) than a Core i3. In addition, i5 processors feature faster clock rates, a larger cache, and can accommodate more memory. Also improved are the integrated graphics.

Read More: What's inside of a CPU?