The LED DLPs should be relatively trouble free compared to bulb based units. I think you are reading too much into your one isolated failure. Depending on what you use your set for, a plasma may or may not be a decent replacement for an LED DLP TV.
How did you get the refund on the DLP anyway?
UMR on HDR vs 4K: The benefit of greater saturation and luminance capability is...not very evident in all images unlike more pixels which can be seen in every scene.