I never took Jackson to obedience classes. I trained him at first by purely just guessing, then I discovered YouTube. I trained Jackson all of his tricks thanks to YouTube! However, he was socialized in many other ways, including going to the dog park, pet stores, and meeting other dogs and people and new experiences on a weekly basis.
So while training from the comfort of our own home was/is GREAT, I still will highly recommend actual training classes most of the time simply for the socialization. I also practiced his commands and tricks outside our home a lot, in order for him to listen w/ distractions. That's the nice thing about classes. Jackson had his first "formal" class in October, and it was an agility class, and I must say... I had a blast and highly enjoyed being able to train and learn with other owners and dogs and am wanting to sign up for an intermediate obedience course just to fresh up and for fun.
I also liked having a trainer be able to tell me what I was doing right and wrong, as sometimes you don't even realize what you are doing.
So, in general, I'd recommend classes! It's a fun experience. And most of it is just like a real classroom, you learn how and what to do, and then practice it at home anyways to 'perfect' it.