To be honest though my main reason for selling Grado is lack of bass extension and very uneven treble quality compared to the LCD-2 (and the LCD-2 is in turn not known for great treble...)
To me the tonality with acoustic instruments was a little off also, but of course tonality is not important for rock music.
Unfortunately my audio descriptive vocabulary was pretty lacking at the time I owned both of these pairs but to be honest the Grado sounds pretty unrefined and compromised for the price.
IMO RS1i does crunchy, guitars and percussion with excellent PRAT but just doesn't sound like $700 level headphone. SR325 is probably more on the money at its price point.
I would only recommend the RS1i if you are a massive electric guitar fiend and don't mind the other shortcomings and questionable value.
In the end I chose LCD-2 because it delivered all the energy rock needs (save for crunchy guitars) without the shortcomings of the RS1i.
I can't think of a genre where tonality is more important.