To people who do quantum computing: are qubits (after error correction) functionally equivalent and hence directly comparable across quantum computers, and is it a useful objective measure to compare progress? Or is it more a easy-to-mediatise stat?
People building these things are trying to oversell their achievements while carefully avoiding making them easy to check, reproduce, or objectively compare to others. It's hard to objectively evaluate even for people who work in the field but haven't worked on the exact technology platform reported on. Metrics are taylored to marketing goals, for example, IBM made up a performance metric called "quantum volume", only to basically stop using it when it seemed to no longer favour them.
That being said, it's also undeniable that quantum computing is making significant progress, error correction being a major milestone. What this ends up being actually used for, if anything, remains to be seen (I'm rather sure we'll find something).
The latter has released quantum computers with thousands of qubits, but these qubits are not comparable with the physical qubits in a gate-model computer (and especially not with logical qubits from one).
Since noone has many qubits, typically physical qubits are compared as opposed to virtual qubits (the error corrected ones).
The other key figures of merit are the 1-qubit and 2-qubit gate fidelities (basically the success rates). The 2-qubit gate is typically more difficult and has a lower fidelity, so people often compare qubits by looking only at the 2-qubit gate fidelity. Every 9 added to the 2-qubit gate fidelity is expected to roughly decrease the ratio of physical to virtual qubits by an order of magnitude.
In architectures where qubits are fixed in place and can only talk to their nearest neighbours, moving information around requires swap gates which are made up of the elementary 1 and 2-qubit gates. Some architectures have mobile qubits and all-to-all connectivity, so their proponents hope to avoid swap gates, considerably reducing the number of required 2-qubit gates required to run an algorithm, thus resulting in less errors to deal with.
Some companies, particularly ones on younger architectures, but perhaps with much better gate fidelities, argue that their scheme is better by virtue of being more "scalable" (having more potential in future).
It is expected that in the future, the overall clock speed of the quantum computer will matter, as the circuits we ultimately want to run are expected to be massively long. Since we're far away from the point where this matters, clock speed is uncommonly brought up.
In general, different architectures have different advantages. With different proponents having different beliefs of what matters, it was once described to me as each architecture having their own religion.
TL;DR: the two key stats are number of qubits and 2-qubit gate fidelity.
Does HN do subscript? I don't think I've seen it. I'm unsure if markdown supports it. I'd probably use subscripts a lot more if markdown had them.