One nice thing about the Viair is that it has a continuous duty cycle.
I'm not sure if the Smittybuilt has that feature.
An old adage, that is so often the case: You get what you pay for...
All the rigs that I wheel with have Viair compressors (various models), and all have worked flawlessly.
'02 Montero: OME suspension, ARB front bumper, Superwinch X9, sliders, 4mm skid plates, telescoping rear light, spare tire Blitz can mount, extended breathers, K&N air filter, BajaRack, IPF lights, Cooper S/T Maxx 265/75/16's, RUD 4x4 Grip Chains