You can read the complete Article #16 and Analysis here:
PS4 Vs. X360 US:
Gap change in latest month: 206,075 – X360
Gap change over last 12 months: 2,671,263 – X360
Total Lead: 1,525,064 – PS4
X360 Total Sales: 28,823,923
PS4 Total Sales: 30,348,987
Very interesting, I wasn't aware 360 was closing the gap, much less by 2.6 million in the last year.
Should be a fascinating race to watch from this point on; the platform totals page has Xbox 360 at 49 million in NA, not sure how much of that is in the US though.
EDIT: Nvm just read the article; "The Xbox 360 sold 45.14 million units lifetime in the US. The PlayStation 4 needs to sell another 14.79 million units to surpass the Xbox 360 in the US."