To wake-up the post and give more information about lowest ISO
I've made a lot of tests this afternoon, and now I've understood almost everything.
So, I've made manual shots (@f3.5) of a colorchecker, 1st 1/4s @ISO80, 2nd 1/5s @ISO100, 3rd 1/6s @ISO125.
All shots are properly exposed (ETTR) and need only a slight correction (max 0.1Ev) to obtain exactly same exposure in LR4.2.
Results: RAW with same exposure exhibit more noise @ISO100 and even more @ISO125, so DXOMark DR results are correct !
JPG doesn't need any exposure correction, exposure really identical, but it's clear that ISO125 is progressively compressed in the highlights, but neither ISO80, nor ISO100, so DPReview results are correct too !
So, if you shoot RAW, use ISO80 if it's possible.
Also noticed that the 2 last patches of my colorcheker were blinking (@ISO80 and 100), but RAW data were not clipped !!!
Have a Nice Day.