I think it depends on the studio and how you like to learn and how good the pros you have chosen happen to be. You will need at least some private lessons to fix real issues and to make faster progress. I honestly wouldn't consider competing without one-on-one with an instructor who knows what they are doing. If you are just going to mess around, have fun and not care how you do...then you can get enough out of group classes.
When I first started dancing I spent alot of time in group classes and learned plenty...now its a waste of my time and energy....and though I mostly work with a professional I still supplement with higher level coaches...who have taught me things he couldn't get through my thick skull.
I have danced for many years and there are still things to learn...you will continue to learn and grow long after you thought it was impossible to have anything left to learn. Dance is magical that way. I think I am doing so well and then I suddenly have a breakthrough that changes everything. For that to happen you have to work with the right people. That means the right location for you....the right teachers for you and people who have real live experience dancing in the direction you want to go. That takes research and trial and error...and be extremely careful if you go with a chain. Sometimes you may find someone good....but the majority of people are just a step ahead of you which isn't really enough to make them decent teachers who can charge at the rate they do. Sadly until you've been dancing for a long time you might not know enough to tell when a person isn't skilled enough to be working with you....which is why a lot of people only work with people who consistently do well in real competitions (Ohio, Emerald, Millenium, Nationals...etc.)
