PS4\XB1 digital share of is 10%, with the XB1 being a bit more than 10% and the PS4 a bit less than 10%.
The digital share for 360\PS3 is only 3 to 5%.
Digital copies are bought more in the US than in Europe.
More physical-digital ratios:
Valiant Hearts - 50-50
Child of Light - 75% digital, 25% physical.
Watch Dogs sales: 2\3 on next-gen+PC , 1\3 on 360&PS3.