His dudeness :
when a Lufthansa A310 called in ready,
Let me guess , early 1990's , whit an ex Interflug captain ?
The bad ones did not last long but caused a lot of problems for a while. Not used to go to busy western airports and not being treated as Masters of the Universe as they were in the DDR)
ATC wise , LH is today definitively one of the best to work with.
As to the debate GA vs Airline, again from and ATC perspective , yep, lots of problems with N and flags of convenience registered aircraft but not with the most GA I would say. Some established airline are far worse.