5.0Trunk:
I have a 6P, Polystinger, and StingerXT ... the 6P is brighter than either the Poly or the XT. The 6P beam is also whiter,IMHO.
That being said, the Poly and XT are both very good, reliable lights. Beams are plenty bright, charging system is well designed, and bodies are tough and resistant to abuse.
I also had the chance to use the original Stinger before I sold it to a colleague ... same praises for it.
The only thing I would consider a drawback is that the Stingers' beam is not nearly as "flawless" as the Surefires'. Otherwise, I heartily recommend the Stinger line.