Regarding geometry, according to the specs, and both measured with a 100mm fork (I believe):
Blur 4X (large)
Head Angle: 68.5
Seat Angle: 73.5
Effective Top Tube: 597mm
Commencal 4X (large)
Head Angle: 69.5
Seat Angle: 73
Effective Top Tube: 579mm
So the Commy is shorter but has slightly steeper angles. Obviously, with the ubiquitous set of Pikes, the angles are going to be a bit slacker all round.
The Commy also has 100mm rear travel vs the B4X of 115mm (if that makes any difference)