Whataboutism vs False equivalence

What is the difference, when does each apply, and can both be at work at once.

Framing and omission

Whataboutism

Answering a criticism by pointing at a fault of the critic or of someone else, so that the original charge is never addressed and the conversation moves to the counter-charge.

Framing and omission

False equivalence

Treating two things as equivalent because they share a feature, when they differ in scale, kind, or consequence so much that the comparison misleads.

The differences

WhataboutismFalse equivalence
MoveDeflection. A charge is answered with a different charge against the accuser or someone else.Comparison. Two things of different scale, kind, or consequence are treated as the same.
Form"What about…?" A question that changes the subject."Both sides…" A statement that flattens a difference.
PurposeTo avoid answering, and to discredit the accuser.To excuse one thing by pairing it with another, or to make a small thing look large.
OriginA Cold War staple of Soviet replies to Western criticism; the word is from the 1970s.A general error in reasoning, named in logic and in journalism.
The counter-moveNote the subject change, answer it briefly if you like, and return to the question.Name the dimension on which the two things differ and compare them on it.
The tellThe reply is about something else.The reply is about the same thing but the scales are wrong.
An example of whataboutism

Asked about the treatment of prisoners, a spokesman replies: "And what about your own country's prisons?" The question is not answered; a new one is opened.

An example of false equivalence

A news report on two candidates' finances presents a bookkeeping error of a few hundred dollars and a multi-million-dollar fraud under the same headline: "Both campaigns face money questions".

Can both apply?

Yes, and whataboutism usually contains a false equivalence: the "what about" only works as a deflection if the thing it points to is implied to be as bad as the thing it deflects from. The difference is in the move. Whataboutism changes the subject; false equivalence stays on it and mis-weighs it. A reply can do both, pointing elsewhere and claiming the two are the same, and each half needs its own answer.