I suspect a combination of the two above.
Ascorbic acid is described by the FDA as a cure accelerator and I would I assume allow more of the nitrate to convert to nitrite but in the end its a case of You pays yer money and takes yer choice.
If your not convinced that saltpetre gives a better taste to your bacon then why use it but on a world wide forum it is difficult to be within the rules of all jurisdictions.
We were informed that the Aussies only allowed 125ppm nitrite and the USA
requires a min of 120 ppm
I suppose that most of us tend to take a "common sense" attitude and keep nitrates and nitrites to a minimum without the risk of undercuring.