Yup, the X1 and PS4 both having an even amount of days to shine in December will be the bigger NPD than this month's mellow November NPD.
December's NPD will be no different to November, it will tell us how many consoles each company shipped to NA.
By all accounts, Sony started production a month earlier, they are producing as many consoles as MS, at the least. We also know a not insignificant portion of stock in mainland Europe is still on shelves.
What will be telling is worldwide sales.
Monday will be a full two weeks since Sony revealed their 2.1m number, indications are they can supply 100k consoles per day, that would be an additional 1.4m. Even with a high margin of era, it's fair to say Sony should have topped 3m by now with relative ease. I also understand there are some Asian launches this weekend too, therefore consoles will have been stockpiled for that.
The interesting question is whether Sony's next sales update will trumpet the 3m sales threshold being broken, or whether they think 4m is possible before the New Year.