Woah ... I think thats a very subjective question.
Of course, I'm inclined to believe that the MB garage would be a better alternative. However, sometimes independant may (or may not) be able to tune it well. I know my local mech. can't tune for nuts.
The good side is, once properly tuned, a W126 tuning can hold for a long, long time.
126 tailed by a 203, 129 leading the pack.