I have had mine for just over a year now and I am very pleased with it. If you want a ceramic Kamado for under $1000, I think the PB is the way to go.
Would I sell a well seasoned 18.5 WSM? Hard to say. Around here I would expect to be able to get so little for the WSM that I would rather keep it, unless I simply did not have the room. If it is one or the other, I would rather have the PB than an 18 WSM. They are a bit of an apples to oranges thing, but the Kamado is more versatile, a much better grill, and with our winters, the insulation makes a big difference. If all you are going to use it for is as a charcoal smoker in moderate to warm weather, I might suggest a 22.5 WSM, otherwise the Kamado is a nice Swiss Army knife of a cooker.