NX 250 has the Dynamic Torque Control AWD System which the AWD system has a constantly variable front/rear driving force distribution ranging from 100:0 to 50:50
NX350 has a new Electronically Controlled Full-Time All-Wheel Drive (AWD) more information on this link:
AWD Link
The electronically controlled full-time AWD constantly varies the front/rear driving force distribution from 75:25 to 50:50 (depending on situation), and uses unique technology to achieve both an optimal contact patch and linear steering feel.
NX350h: AWD E-Four has a constantly variable front/rear driving force distribution from 100:0 to 20:80 percent modes.
NX450h+: AWD (E-FOUR) with constantly variable front-to-rear torque distribution between 100:0 and 20:80 percent modes.
Does not look like there is side to side distribution. I guess they don't think you will heavily bring the NX off-roading.