Mirko har already explained this here in this post: http://www.apug.org/forums/viewpost.php?p=1394949

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So compared to APX you will get more DMAX and a slightly higher contrast apart ofcourse from the different base.
This is why we formulated the Silvermax developer with it. This developer is soft working similar to our ADOTECH developer and optimized for Silvermax.
If you use both you get instantly very good results and (hopefully) can see the difference to "normal" fims.
While "normal" in this context means a film designed as a negative film with just as much coating (silver cotent) as nevessary to achive good DMAX for regular printing work
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No one will market a new product without wanting it to sell. I am happy for any new analogue product, and I will certainly test the new developer to see what it does. But I'm sure D-76 will work fine.

Trond