The 2020 M just got a face lift. Out of all the coloured version of the 2020 M the PhantoM is said to have the toughest coating.
New to the 2020 M is a captive cap which means the cap doesn't need to be bent into as much of an oval shape as all other caps made by dynavap. Another very handy feature to the 2020 M is the mouthpiece now has a built in 10mm joint making connection to bubblers a lot easier. On top of that the airport is now split into 2 slits making airport adjustments more controlled. And finally the other functional change to the 2020 M is the stainless tip. It is now adjustable by 50%, basically halving the bowl size of your M.
Besides the functional upgrades the other very obvious change is the appearance. Dynavap have really taken the M to another level once again. There is a lot going on but it doesn't come across as too much.