Welcome to the NICOClub Forums Konstantin!
My recommendation?
None of the above!
Everyone drives their vehicle differently and under varying conditions. While a 6k mile OCI (oil change interval) might work for someone who travels a lot of highway miles, it's a different story for someone who drives in short trips in the city.
The BEST way to determine if the oil is right for your vehicle and type of driving is to perform an oil analysis:
Blackstone Labs (USA):
http://www.blackstone-labs.com/
WearCheck (Canada & USA):
http://www.wearcheck.com/
Just follow their advice on when to sample the oil and go from there.
If you want some advice, then post your used oil analysis here and then maybe we can comment.