Which etching process is better, photochemical or electrochemical?
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.