Both can be useful - it depends on the situation. If you want a job, you might need a degree or formal qualification. Self tuition is very important to enriching your personal life, or answering questions you have about life, philosophy, religion etc etc. Self tuition online isn't very sociable, so it can also be better for your social development if you actually go to class. You probably need a combination of both types of learning to be a truly educated individual.

i think attending classes is better but if you want to practice you can also use self- directed learning

For me, it is better to attend courses because it will be face to face. But, I recommend you too to also at the same time, learn in the internet.. Both will be a great help :)

As a teacher I see better results in students attending classes, whereas online you don't have access to any personal help. If you're not self motivated to learn, online classes won't help you pass exams.