A i5 will have 4 full cores.
A i3 will have two cores plus hyperthreading.
Hyperthreading uses unused cycles of the main cores to dispatch two additional threads, giving the appearance of 4 threads. But... since a hyperthread is using only part of a core, it will be perhaps only 25% the power of a full core.
The FX 8350 chips are advertised as 8 cores. In actuality, there are 4 modules with two cores each that share some resources. Not unlike hyperthreading if the shared resources are needed by both tasks. In essence, I see a FX8xxx ad a hyperthreaded quad core with hyperthreading that is perhaps 80% effective. Not bad, but not perfect either.
More importantly, the intel architecture has improved so that an intel core is perhaps...