Answer: neither. It was 1.44 x 1000 x 1024 = 1,474,560 bytes.
The reason was that the standard density single sided 3.5” disk took 360 KB, back then when KB usually meant 1024 bytes (the IEC standardized KB to be 1000 bytes only in 1998). This doubled to 720 KB when the disk was used double sided, and it doubled once again to 1440 KB when HD was used. And then 1440 KB was turned into 1.44 MB, thus mixing the 1000 and the 1024.
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