Over the years I have done a number of big organised tours which, on the whole, have been good fun. The advantage of these tours, for me, is that all the tough decisions have been made for you and you are free to ride and socialise (or not) during the day. There is also the reassurance that if anything goes wrong there are people to sort it out. However, these things come at a cost and, on the whole, were something I could justify when working full time.
With the internet, researching and organising tours are now much easier I now prefer the freedom that cycletouring on your own gives you. Whilst I do sometimes miss the social side, being on your own means locals are much more ready to invite you in for coffee / chat etc. and there is more freedom to change plans etc.