I personally wouldn't waste the time, effort and expense of swapping the DTUK box over for the MTM. They are much the same and neither are a proper remap, the MTM box is expensive too and I would stick with what you have.
My opinion of these boxes is that they are good for stage 1 type stuff but if you want to go further, you will probably need a mainstream tuners remap. The tuning boxes have their limitations, there is only so much boost you can manipulate, you then need to channel into timing and fuelling changes to get the best from your hardware. Something the tuning boxes are not capable of.
However, I am going to run stage 2 mods on the tuning box initially to see how it reacts.