From the discussions I recall on this in the past, the advantage of stainless steel is that it collects less gunk due to being less reactive to things like acid etc. and therefore it is more resistant to build up and problems, requiring less breakdowns and full cleaning unlike brass/copper stuff. I use a mix of both types and so far haven't had problems but I think I'm due for either a good cleaning through the system or disassembly and cleaning... either way its all about the 'ease of clean up' as far as I recall.