omg, some people.
additionally, the 2MX is an updated core with more features -
the CORE is faster and can process more than the DDR - the memory is not.
They will perform on par until you get to
a) applications with HEAVY memory use
b) High resolutions
IMO, go the MX - as I said, updated core, with support for more feautes - which you may find yourself wanting in the future, where the DDR does not support them.