Phaetons have solid wood cabinetry fronts-only. The doors and frames are solid but the rest is wrapped.
Bus = 425 HP Cummins 8.9 liter ISL with 1,200 ft-lbs of torque, engine compression brake, IFS, side radiators, choice of either Freighliner, Spartan, or Powerglide chassis.
Phaeton = 360 HP Cummins 8.3 liter ISC with 1,050 ft-lbs of torque, exhaust brake, solid front axle, rear radiator, Freighliner chassis on 36-40' coaches with Spartan on the 42' tag axle coaches. Powerglide chasis available soon under the Phaeton (but no IFS or side radiator).
Bus has other bells and whistles. The paint stripes extend onto the sides of the slideouts wheras the Phaeton has plain slideout sides. Hardwood cherry cabintry throughout wheras the Phaeton has hardwood doors and frames with the rest wrapped. Solid surface counters everywhere on the Bus but the Phaeton has the dinette table and non-galey counters as laminated with solid surface edging.
Bus has Smart Wheel, keyless entry and compartment locks, etc as standard but none of that is available on the Phaeton. Also many options, such as AquaHot heating are available on the Bus but not on the Phaeton.
Lastly - the Bus costs more than the Phaeton. They are both excellent coaches and great values within their price points. You can't go wrong with either. Just pick the one that you like and can afford and go for it.