@NR4P, not sure if you are considering a new or used model X with 100 kWh battery. The newest model X’s can take advantage of the 250 kW of the V3 super chargers but older ones can not. I am not sure the time frame in which that changed. My end of 2017 MX has been limited to 150 kW max. That being said, though, after a recent software update I did pull slightly more than 150 kW from a V3.
I have one trip I do a lot and have Teslafi logs for both my M3 and my MX. The short answer on how they compare is that my MX takes 5-10 min longer per stop. Here is a concrete set of data from my 2 SC stops with each car, all 150 kW SCs, trips with pretty similar conditions.
SC1: 2018 M3 19% to 63% in 18 min
2017 MX 19% to 63% in 22 min
SC2: 2018 M3 16% to 77% in 26 min
2017 MX 18% to 70% in 31 min
My current range on the M3 is in 290’s and the MX is about 280 miles, so the % SOC are reasonable comparisons.