Honestly, I think if you are the kind of guy that like to sit outside all day on a saturday, cooking up a butt and some ribs at a solid 225-250, then the WSM is for you.
Now if you are like me and like to cook during the week, get the PBC. The thing runs hotter and cuts down on cook times a LOT! I did a 5lb shoulder in about 4 hours on mine. Might be a later dinner than usual but its worth it. Or you can do a full rack of spare ribs in about 3 hours. Or fantastic chicken in about 1.5 to 2 hours. Or throw the grate in and do brats and burgers with a half basket of charcoal.
That's another thing! The WSM has a massive charcoal basket. The PBC's is pretty small. One load of charcoal in the basket of mine burns hot enough to be usable for a solid 10 hours, which is longer than you will need to cook most cuts of meat at 290*. And it did the 10 hour thing when it was near 35* outside.
Either are good choices though! And unlike others have said, I still use my UDS. For me it boils down to using the PBC on the weeknights and the UDS on the weekends when I have a whole saturday to spend outside. The PBC is great but I still love my low and slow.
18" OTS, 22" OTG, SJ Silver, Cimarron Offset, Coleman Bullet, PBC, UDS, QMaster ATC