I am not sure about the differences between the A type vs the C type.
On spec sheets the current voltages look a bit different, but nothing I can see that makes a huge difference.
What are the differences?
I have found a problem using these regulators.
I found I had to decouple the output of the regulator with an electrolytic very close to the regulator or I got instability on the reg output.
Perhaps I just bought cheap versions.
It used to be standard practice to put a 1uF tantalum capacitor on both input and output of the 78xx and 79xx regulators.
The datasheet says you dont need a decoupling capacitor on the output.
Yes, I think that you are putting too much faith in spec. sheets. Manufacturing techniques change with time, mfg. seldom update the spec. sheets.