The thing to remember with DMT's is that they don't recommend using anything finer than the 325 for flattening. In fact they recommend the extra extra coarse for hard Arkansas stones. The 1200 DMT can be easily turned into plain steel bar with excess use on hard stones.
On the other hand the 1200 Atoma plate works great as a slurry stone & light lapper. I have personally seen a 1200 Atoma which is still in use after approx 10 years.