I have both. It partly depends on what you plan to use the knife for.
I am pretty dissapointed with the heft of the steel on the M390.
It's almost half the weight/substance of steel provided on the D2, and compared to the many other Benchmade designs I have.
It is much easier to sharpen and holds an edge better than the D2. For skinning this is not the knife I would use.
For the amount of money your spending on m390 you can get the Benchmade Skirmish in S30V which has a superior locking mechanism in my opinion, is easier to sharpen and a larger more useful blade.
I find that the axis mechanism gets jammed with grit and dust too much.
Note I have and carry all these blades.