Now 8th gen i3 too have overclocking upto 2.4 ghx (same as i5).
i5 has lower base clock of 1.6 vs 2.2 in i3.
i5 has 4 core vs 2 in 3.
Previously i5 used to shine as it has higher turbo boost while i3 had none but in 8th gen even i3 has turbo boost.
So for a basic user is i5 8250u worth it ...