I think think both positions of the AH VS WH discussion have their merits .... WH is definitely better for comparing systems with different voltages .... but, for me, it is what your mind has gotten used to recognizing.
For instance, if you grow up your whole life thinking in Deg F and then have to start thinking in terms of Deg C.
Once you get used to thinking one way, it is hard to think the other way.
It's not one or the other though. If you do capacity testing, by all means use Ah since you eliminate errors due to losses in wiring etc. However, if tomorrow someone comes to the forum and asks "How much power (sic) do you use every day?" - makes little sense to answer "5 Ah" without a lot of context. Instead, just saying "3kWh" makes the answer very clear. I use both terms, but context matters.