There's a few of us here on these forums that regularly play games on plasmas and screen burn is not an issue (despite for myself, falling asleep and leaving a static game image on the screen for 6-8 hours at a time). You may get image retention every now and then, but this is a very different beast from screen burn and does not affect the gaming experience in the slightest.
I can't advise on those two sets, but just to let you know that screen burn is not a concern on modern plasmas under normal usage.
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