People often said the MS2 is brighter but having both MS1 and MS2 I don't agree on that.
MS1 is good and I have no problem listening to either one of them any time. MS1 mid range is more grainy and forceful while MS2 is buttery smooth.
Forceful mid can sounds good too, MS2 is more relaxing. It is like old whiskey while taste the same, it is smoother to swallow.
MS2 is much more detail but I also find MS1 is detail enough and MS2 price cost 2x more. Some modern tracks are optimize for general earphones so MS1 can sounds "bright" for this instant.
Then using others earphone/headphone on this badly recorded tracks does have the same problem. Most of them sounds ear piercing while the Grado's sound more "ringing". All I have to do is to lower the volume. So I think it is not the fault of the headphones but the recorded tracks itself. MS2 "ringing" is less tiring as they are smoother, does that mean it is less "bright"?
I think so. It is not as bright as MS1 just smoother, more detail and to some it just sounds "brighter". I think it is the same old whiskey just older and smoother
But like I said, because I have the MS2 if not I have no problem listening to the MS1 at all.
I have the MS2 because I got a use pair around $150, something I cannot pass and of course better than MS1.