I would argue that the m50x is better, I had an older version of the corsair headphones and replaced them with the m50x and I must say that it was a huge difference. First the m50x is more comfortable and you wil have an easier time wearing for long periods. Second the audio quality is much better. And third you can use an upgraded dac later on for even better audio quality.
for the m50x you are basically paying for the drivers. Where the void pro is drivers, transmitter and dac, which will cause the drivers to be cheaper than the m50x.