I think it's great to have both as they compliment each other very well. It's useful to have classes with a teacher/tutor who structures the classes properly, gives appropriate homework and creates classes based on the student's needs. It's also great to practise informally as this is a great opportunity to practise, as well as being great fun. For teachers, tutors or language partners, the most important thing is that they are friendly, patient and encouraging so that you can enjoy the learning experience :)

So long as they are the kind of teachers that can please me, it doesn't matter what type of teachers they are.

Depends if you want to pay or not. Complement each other.