Electronics Foam etching or the conventional way?

If I were to buy an etching machine for making PCBs would you recommend heated foam etching machines or the conventional heated ones using air bubbles? What are the advantages and disadvantages of both?

 

*Bump*

If I have somehow mistranslated the names of the etching processes or something, here are some pictures:



Conventional heated etching with air bubbles



Heated foam etching

 

Somebody?

 

I have only tried the conventional way... can you explain the foam thing? how it works...

 

Well the foam etching machine first heats the etching solution and then pumps it through some special pipe thingies, which create foam. This etching foam then comes in conact with the PCB and so etches away the copper.