Hi Markus --
The characteristics of a desirable trading system are 
  yours to decide.  Whether you want to focus on trend following systems, 
  on mean reversion systems, on pattern systems, statistical systems, or 
  whatever else is completely up to you.  
I meant no 
  criticism.  My suggestion about allowing the relationship between the two 
  moving average lengths was simply to point out that what was originally 
  thought of as a trend following system might transform itself into a mean 
  reversion system under some circumstances.
As always -- do your own 
  research, including in-sample testing and out-of-sample validation.  Walk 
  forward testing is extremely valuable.  In-sample results are always good 
  and have no value in estimating future performance of a 
  system.
Thanks,
Howard