A:AnswerThe M65-C1 lacks HDR/Wide Color Gamut/Extreme Black Engine tech. The M65-C1 is centered around 4K, where the M65-E0 is centered around 4K + HDR. There are other differences as well with the C1 and E0 with refresh rates, see below:
https://www.vizio.com/m65c1.html
A:AnswerThe M series uses a VA panel which is not as good as the IPS panel used on the P series. Also 32 local dimming zones versus 128, which will make the P series brighter and allow the colors to pop more. P series have more HDR compatible HDMI ports as well.