Not knowledgeable on those specific year models. We did, however, last week just purchase a 2003 Phaeton with the CAT 330 HP diesel. It's 29,410 - GVWR 25,553 - Unloaded Weight with fuel.
It has 3 sliders and an Onan diesel generator that slides out the front.
With 50 gallons of diesel, no water in the fresh water tank I can say that it has no problem power wise. On one of the first trips driving it with my wife following she complained that I was driving too fast.
While there's many differences from a 2008 to a 2003 Phaeton I do know that a couple of people in the RV business commented very favorably on the Phaeton. There were alot of nice details I noticed in the 6 days we've had it. The under body of the motorhome is insulated, fit and finish seemed good.
Test drive both, take a look at the layout, features and see which one you like the best.