There is still some mis-information in this thread.
Neither the Aronson stack or Mnemonica are "more random" than the other. Both have features that a lengthy, close examination by a knowledgeable person could uncover.
What's more important though is that they both look completely random to a casual observer, even one given a few minutes to study them.
Mnemonica can be reached from U.S. new deck order (A-KH, A-KC, K-AD, K-AS) using several long runs and 5 faro shuffles (1 is a partial deck faro). It was designed to be reached from Spanish new deck order, which simplifies and shortens the process significantly. There doesn't appear to be any easy way to reach Aronson stack from new deck order.
The Aronson deck was designed from the ground up and includes many built-in effects (Poker deals, bridge deals, etc). Mnemonica was primarily built using a process to get into it (the faro shuffles, etc), and then most of its effects have been discovered after the fact by Tamariz and his students.
Both are powerful tools and while you may prefer one or more of the "built-in" effects in the Aronson deck, their strengths as "open index" decks (where you know the exact position of every card) are identical.
I first learned the Aronson stack in 1996. I used it for almost 10 years before switching to Tamariz. The only reason I switched is because I was proofreading for Stephen Minch and wanted to know the stack as I was proofing the book.
I never used any of the Aronson built-in effects, so losing those wasn't a problem for me. But...being able to get into my stack from NDO was wonderful. I use brand new decks quite often, and this feature alone was worth switching to Tamariz for me. If you're the type to use the same deck for days or weeks on end, that's probably not a selling point for you. It was for me in a big way.
Jason