In my opinion it does not matter whether you choose a conventional course or decide to learn on your own using self-study courses and all the help accessible on the Internet.
The point is to choose the method and the way of learning which suits you best.
Some people like regular hours of learning and feel good even in big classes, some people don’t. A couple of my students used to say they were too lazy to sit at home and learn on their own. They found it boring. They enjoyed studying with other people because they had an opportunity to speak and exchange their opinions. I think a lot depends on a teacher. A good teacher - of course I have myself on my mind;) - tries to get his class interested and involved in a ‘real’ situation taking advantage of students’ imagination. That is why I think studying English in a group may be efficient particularly with teenagers and students.
Elder people start learning because they usually MUST to keep their job or to get any job. They don’t believe in themselves, think they have bad memory and that they will die before they learn (that is my own opinion about myself too) ;). When they break first ice, everything is OK. But forcing them doesn’t make any good, and it doesn’t matter if the course is paid by the employer, a foundation or by the student himself. Learning must be a pleasure.
Learning in the class is not a good idea for busy people who have little free time and not regular working hours. Some persons of high standing find learning in a class very stressful too because they are not used to being corrected and making mistakes in public :).
Even though I have nothing against studying in a class, I personally prefer studying on my own. I have never used any course books but if I had been born later I would have :). There are so many interesting English courses nowadays and everyone can choose one which suits him. The only point I’m aware of is that most of the courses are so much concentrated on communication skills. That is OK and the most important thing, but their authors sometimes do not take under consideration that you need writing skills as well as clear grammatical information. You never know if it will not be necessary in future, when you decide to take any examinations and get a job of a ‘letter writer’ with a company.
When I started learning English– fortunately it was in the States, where I went not knowing English at all - I had only two good grammar books and two good dictionaries: one monolingual and one English-Polish. At the beginning I simply translated some sentences which were necessary for me to talk with a boss and my Irish friend at work. She agreed after years that it had been a great fun for her learning at the end of my monologues that I had been talking about the past event in the present continuous tense :). So maybe it is the best idea to go to an English-speaking country for a year or two? Start with a job which doesn’t require any qualifications and then change it for a better one, already knowing English.
What I personally like about this forum is that I have an opportunity to check my vocabulary, learn more of it in a pleasant way and at the same time have a contact with other people from all around the world. Shortly saying it is much more enjoyable than studying from a course book or writing essays which no one is going to read.
Summing up, I got used to studying on my own but … I sometimes lack a teacher to correct my mistakes and assess my progress. I would greatly appreciate if you did it here for me taking under consideration that no teacher likes being corrected ;).
Forgive me the length of my monologues and ‘productivity’ but I’m just practising writing 700 words in two hours for my exams ;). I think I could write a book on this subject but I promise not to do it here…