Group all the way for me.
There's no way I'd be successful on my own. With group you get hints, tips, support and motivation.
Yes you get that on here and there are some wonderful people on this forum, people with whom I'm sure I'd be friends in real life BUT you don't get the support of a consultant, the up to date information and someone weighing you each week.
I need the "threat of the scales" to keep me going. I know that by Friday or Saturday, if I've been a bit off plan, that I need to start pulling it back a bit ready for Tuesday. If I did it at home, I'd be more inclined to think "stuff it" and leave it another week.
I know some say that if you are focussed you'll lose weight on your own, but not for me.