ChipFlip
The Core i5-13400 costs $37.96 more than the i5-12400F used, $162.95 against $124.99. Both are Intel's mid-range pick from back-to-back generations. The 13400 has an integrated GPU the F-suffix 12400F doesn't. Is that the whole story, or is there more to the gap?
Same core count, different chip underneath
Both chips run 6 performance cores plus additional efficiency cores on the 13400's side, since it's built on Intel's newer hybrid architecture. The 12400F is a straightforward 6-core, 12-thread part with no efficiency cores at all. On paper the core counts look close. In practice the 13400 pulls ahead in multi-threaded work because of those extra E-cores, even though its performance cores aren't dramatically faster clock-for-clock.
The missing GPU actually matters here
"F" in Intel's naming means no integrated graphics. That's fine if you already have a discrete GPU and never plan to troubleshoot without one. It's a real problem if your GPU dies, you're building a temporary rig, or you just want a display output for BIOS access without digging out a spare card. The 13400 skips that risk entirely.
Where the 12400F still wins
Price. $37.96 buys a lot of headroom elsewhere in a build, and if you're pairing either chip with a discrete GPU anyway, the missing iGPU costs you nothing day to day. For a pure gaming build where a GPU is already locked in, the 12400F is hard to beat at this gap.
Bottom line
Buy the 13400 if you want the integrated GPU as insurance or expect heavier multi-threaded workloads. Buy the 12400F if a discrete GPU is already part of the plan and you'd rather keep the $38.