> I am guessing since the MKH 60 has a bit "wider" pattern than the 416, that is why it makes for a better choice.
No, if shotgun microphones could have a consistent pickup pattern across the audio frequency range the way people seem to imagine, they would be enormously useful for distant pickup of all types of sound. The narrower their pattern, the farther away you could use them from.
Unfortunately, though, that isn't how shotgun microphones behave in reality. Even the best have irregular high-frequency response off-axis, and not just a little--multiple peaks and dips of 4 - 5 dB are not uncommon. And the high-frequency response also varies greatly depending on the exact angle of sound incidence: A frequency that has a 4 dB dip at a 30 degree angle might have a 4 dB peak for sound arriving at 35 degrees. That's due to the physics of how shotgun mikes work (the "interference tube" principle).
If you were recording in a dry acoustic and all your sound sources were on axis, this wouldn't matter much. But when you're recording music at normal distances, half or more of the sound energy that reaches your microphones is coming from significantly off-axis. In such situations, shotgun microphones (especially long ones) color and distort the sound picture considerably.
One other, equally important point: The narrow directional pattern of a shotgun microphone occurs only above some given frequency--perhaps 1 or 2 kHz, depending on the length of the slotted interference tube of the microphone. Below that frequency, the interference tube has little or no effect and the microphone's directional pattern will be a conventional super- or hypercardioid. For normal applications--mono dialog and effects recording for film and video--that's OK, but for stereo music recording it's not. It means that the stereo imaging of your M/S arrangement will be quite different at different frequencies. Off-center sound sources will divide by frequency, with the lows and low-mids coming more from center while the highs will come more from the sides.
For M/S stereo recording to work, what is needed from the "M" microphone is the greatest possible consistency and smoothness of directionality (whatever directional pattern you may choose) across the audio frequency range. Unfortunately, those are precisely the qualities which shotgun microphones, as a class, are notably deficient in--particularly long shotguns. By contrast, a good single-diaphragm supercardioid (Schoeps, Neumann or Sennheiser) will have a far more even (constant) directional pattern across the frequency range. And if you absolutely must record from a substantial distance, that type of microphone will also give you much better high-frequency diffuse-field response than any shotgun can.
So that's why.
--best regards