The thread confuses two different [albeit seemingly similar] roles. Troi is a counselor and Guinan is not.
Troi is no doubt qualified, has numerous 'sessions' which we never see and is generally good at her job. She helps numerous people throughout the show to overcome certain tragedies in their lives.
Guinan is worldy. She is wise. She isn't just a bartender, she is a centuries old woman who has no doubt seen a lot of stuff. Your little love-life problem or ethical quandry is likey nothing she hasn't seen before. She has no qualifications but she is a damn good source of opinion and a useful measuring stick to keep you grounded and on track.
They provide a similar service but it IS different. You wouldn't walk into Troi's office and ask "How do I get girls to like me?" in a similar way you would not walk up the bar and say "My brother just died on Earth and my whole world has just fallen apart" while bursting into hysterical tears.