Ok here is my opinion of the two sets.
The XBR will be a brighter picture, with still images be a sharper image, have no glare off of it and no potential for burn in at all.
The Pioneer will have the most accurate color, best with fast motion, and the best black level of anything I have seen out there right now.
Outside of 9-10 feet your eyes won't notice that it is a 720p set on the Pioneer.
Both of these units have VGA connnections to them so hooking a pc to either one is no problem. You will here people talk about burn in on a plasma. The most critical time is the first 200 hours on these units. Dropping it to its optimum mode makes the set look much better and helps to prevent burn in. The other thing that Pioneer does is use a feature called pixel orbit. This lets the pixels shift their image so to help preven the burn in of a static image.
I have the 60" 1080p Pioneer and play my PS3 on it all the time.
Either way you go they both are the best in there class.
If I can help you out let me know. [email protected]