Yeah, the blacks are not even close to black on the the plasma.
That seems odd to me, perhaps it is an age thing related to your specific tv. but isn’t deep blacks one of the things plasma does better than lcd?
You’re missing a generation in the middle. Old school LCD’s were TERRIBAD at blacks, the best they could do was a glowing blue/gray. But then the TV makers figured out they could divide the backlighting into zones and once they got good at it, blacks got MUCH better on LCD’s.
Panasonic was known for it’s “deepest blacks of any plamsa” but no, plasma blacks aren’t quite true black. Though they are good enough that you have the lights in the room completely off to notice an issue.