I have both. Well the MDR 1 RBT.
The Ex1000s are great the best IEM ive got, but for them to sound like the MDR you need a really good seal and good sound source. I tend to use Comply Foam Tips, and then pipe that from Iphone into a Fiio amp then to headphones.
The MDRs are more forgiving and to be honest very good headphones, i also have momentums and Amperiors none of which come close to it.
The EX1000s are very clear some may say too crisp, but i like treble other warmth, the bass is very good also, but not as deep as the MDRs
Also bare in mind the EX1000 will be rare soon, and as some say probably one of the best IEMs of its form factor out, so maybe worth the purchase.
I do prefer the EX1000 just because they are more portable, but the MDRs are much more comfortable.
hope i helped a little :)