Apparently the "battle" is won by Perry. The expectation is that it ends the week by having sold nearly 450,000 copies, far more than Gaga, with 200 or 250 000.
Remember that the single Perry is being sold longer than the song of Gaga - the release was advanced after the song was leaked online.
Actually "Applause" also came out ahead of schedule for the same reason - the song was scheduled to be launched next week.
The final outcome of the battle will be known by next Wednesday (21), when the Billboard revealed the result next week.