between a 3rd gen corei5@ 2.5ghz and a 4th gen corei5@ 1.6ghz, which is better?

The diffence between 3rd and 4th gen is hardly noticeable(even with the same ghz)


but in this case, if the rest of the pc specs are the same i.e same type of ram, storage, usb ports(because in some cases 4th gen pcs comes with newer technology e.g, usb 3.0/3.1, M.2/SSD ports), i'll go with the 3rd gen because of higher clock speed, which in short mean faster responsew and performance in apps.

CapedBaldy:
between a 3rd gen corei5@ 2.5ghz and a 4th gen corei5@ 1.6ghz, which is better?

Clock speed is not enough to judge. The one with lower clock speed might have turbo boost. It might also be a quad-core CPU. I would prefer a quad-core CPU with a lower clock speed compared to a dual core. Asides that, it might have hyperthreading which might make it faster. If it is used in a laptop with integrated graphics, the HD graphics of the 4th Gen i5 might be better than that of the 3rd Gen i5.

Anyway, your best bet would be to compare the CPU's side by side with Google.