Which etching process is better, photochemical or electrochemical? My boss and I are experimenting with several different ways to micro machine .01" and .005" stainless steel. When I look up how it's done professionally, I see an overwhelming majority of companies use photochemical etching (acid etching). I have also seen electrochemical etching as an option, but not as a "precision" method. So far, both methods have achieved sub-millimeter precision and electroetching currently takes a slight lead over photochem, but neither have achieved the incredible accuracy that I've seen online that appears to have resolution finer than the human eye can distinguish.

Electrochem etching has also proven to be much simpler and safer since we don't have to be involved with potentially dangerous chemicals. My suspicion was that acid etching would be more precise since it is so widely used, but our results are not supporting that hypothesis. I am wondering what advantages does acid etching have over electroetching that makes it so much more popular? I'm curious to know more so we can further refine our etching process.
While I have no expertise in this subject I did a web search for "advantages acid etching has over electroetching" which led to the following which I copy verbatim, specifically the part that seems relevant to your comments:


  Electro-etching offers a great alternative to etching with acid, but
  as with everything, it also has some disadvantages: 
  
  • A feature of electro-etching is that it will bite isolated lines deeper than those that are close together, or cross hatched lines.
  Also it tends to bite harder in the external areas than at the center
  of plates (edge-effect).
  In addition, electrolytic etching bites harder on the edges of wide
  lines and edges of resists of large areas of open bite. This is more
  noticeable in prolonged bites. However, all these drawbacks can be
  compensated for by using a cathode grid in the electro-etching unit
  instead of a cathode plate.