Looks good. There's indeed a big difference in the reflections between SR and PTR, but I like the ambient light in SR. Somehow I often don't like the very dark shadowy areas in a PT render, although it does add mystery, there's a lot hidden in blacks.
I did some more testing yesterday with the alpha and color black method, but in SR it doesn't work, and in PTR it makes no difference if you add the constant shader or leave it out, as far as I could see. Perhaps the PTR already eleiminates any shadows from the glass part.
Regarding EXR; I've had a few instances where the lights indeed seemed a bit burnt in local areas.