You should not forget, that the result depends heavily also on the listener. Probably the hardest to understand English I have ever heard has been spoken by two

You should not forget, that the result depends heavily also on the listener. Probably the hardest to understand English I have ever heard has been spoken by two native Englishmen who I met last year at a hostel in Spain. Similarly in my opinion the most clear English is spoken in Germany and the Nordic countries. It's just a matter of what you are used to.