Mi a különbség a present perfect és a present perfect continuous között?

Az angol könyvem az alábbiak vannak.

Present perfect:

-For actions which started in the past and are still continuing in the present. He has been a car salesman since 1990. (He started working as a car salesman in 1990 and he still is a car salesman.)

-For actions which have recently finished and their result are visible in the present. They have done their shopping. (We can see that they have finished their shopping because they are leaving the supermarket and there are bags in their trolley.)

Present perfect continuous

-An action which started in the past and continues up to the present. Mr Davis has been teaching for six years. (He began working as a teacher six years ago and he still is.)

-An action which has recently finished and its result is evident now. They are tired. They have been painting the garage door all morning. (They have just finished painting and the result is evident now. The paint on the door is still wet and the two people look tired.)

Csak én nem érzem a különbséget vagy tényleg nincs? Melyiket részesíti előnyben az angol?