In your opinion which is better? The 111 or the 500M and how much better?
I think I know the answer but your have both of them there so let us know.
Are we talking mostly the low level glow from a black screen or overall with normal programming?
Honestly, the biggest advantage I've seen in going for the 500M is in the lack of DSE. My 111 had what I would call light to moderate DSE. It didn't bother me at first but it's become increasingly annoying over time to the point that when conditions are right to see it, I can't tear my eyes away from the problem. The 500M is essentially perfect in this regard, and for me the purchase was worth it for that alone. As I have never seen a 111 that did not suffer from the problem to some extent (most were worse than mine), I'm making a guess that it's been addressed with the "newer tech" panels.
As far as black levels go, the difference is clearly seen on a black screen and while watching lower APL material. The dimmer your room the bigger the difference becomes. I would not, however, sacrifice ISFccc for the improved blacks between the two.
Thus, if you want to make 100% sure that your warranty remains intact, then there'd be little question in my mind that you should keep your Elite.
Your mileage may vary.