Nottingham simply needs to be kept on the colder side in order to be considered clean. S-O5 is well more heat forgiving in this regard. That is (in my opinion) why in comparison of the outcomes of these two, S-O5 often wins. I.E. Nottingham fails to live up to S-05 because people treat it as if it actually is S-05, when it is not. Nottingham can be successfully used as an ale yeast substitute for lager yeast, and will ferment at 50 degrees F. If kept at or below a cut-off point of about 62 degrees (at most) it is clean. It simply is not SO5 like as to its temperature profile, and Lallemand does it a major injustice by implying otherwise.
PS: If you simply pitch Nottingham in a refrigerated environment maintained at 62 degrees, it will heat the Wort to potentially as high as 72 degrees, and it will fail and taste awful. The Wort itself needs to be actively maintained at (or below) 62 degrees for Nottingham, not the air environment around it. It also does not explode and head out the blow-off tube when so maintained. In fact, at the proper temperatures it doesn't even need a blow off tube. If you see it heading out the blow-off tube, this is a good indication that the beer will taste "off".