Too low of Hz, and rotating machinery is effected by slow speeds + Lighting will have distinctive pulsations.
Low Hz also requires larger core /coil setups for Inductive machines (Induction Motors, Transformers, Ballasts, etc.)
Higher Hz causes Induction Motors to have a higher fundamental rotating speed, plus core/coil sizes are reduced.
Lower Hz - Lower Xc but increase Xl, Larger core/coil designs but lower Skin Effect;
Higher Hz - Lower Xl but increase Xc, smaller core/coil design but increased Skin Effect.
50/60 Hz is something that was a "Happy Medium" between George Westinghouse's equipment builders and Tesla's Engineering specs. From what I remember, Tesla wanted to run around 100 Hz, or higher - but was "forced" to Engineer the equipment's specs for 60 Hz.
50 Hz is not too different from 60 Hz, but both are way off the scale when viewed by 400 Hz.
BTW: Fluorescent Lamps are much "happier" when they are driven with High Frequency AC, as opposed to driven by 60 Hz AC!
Drive them at 40 KHz instead of 60 Hz and they will "Smile"!!!