I've always assumed "giga" is capitalised because it one might confuse a lower case g for "grams". Technically, 1gm is one gram-meter (grams * metres), whereas 1Gm is a thousand kilometres. You don't often encounter weird combined units like gram-metres outside of physics, except maybe for kWh (kW * 1 hour), but I don't see why you wouldn't be nice to physicists and give them the extra clarity.
Other order of magnitude indicators are capitalised to distinguish them from their smaller counterparts (millimetre/Megametre).
Wikipedia states that the distinction is because units named after a person always start with a capital letter. I've always assumed Hz has to be capitalised to prevent confusion with the hecto prefix (hHz being 100Hz). I don't think there's a unit or order of magnitude that's abbreviated to `z`, so in theory "Hz" could just be "H",
I think Hz is more readable, but that's probably because I'm used to it.
I had structural engineering and electronics in school and especially when you get compound units like Nm (newton meters) not wondering if the N is a newton or the SI-prefix nano is not nothing.
In the end the reason for the weird capitalization is just to avoid situations where that ambiguity will occur.
I remember me and a friend asking our physics teacher if it wasn't a problem that tera (T) and tesla (T) were the same symbol. He looked at us, paused a bit, then explained how absolutely enormous a terra tesla would be, and thus why that isn't actually an issue :P
Other order of magnitude indicators are capitalised to distinguish them from their smaller counterparts (millimetre/Megametre).
Wikipedia states that the distinction is because units named after a person always start with a capital letter. I've always assumed Hz has to be capitalised to prevent confusion with the hecto prefix (hHz being 100Hz). I don't think there's a unit or order of magnitude that's abbreviated to `z`, so in theory "Hz" could just be "H",
I think Hz is more readable, but that's probably because I'm used to it.