This summer will be our first cruise for my 40th birthday there are so many different types of cruises out there that it is hard to pick we too didn't want too formal affair but didn't want a laid back cruise either so we picked princess cruises.yes the cunard fleet are impressive but there are parts of the ship that only certain class of passengers can access and we didn't like the sound of that.i think the reason we picked princess over p&o was the sailing dates to coincide with my birthday to the itinerary we wanted.i'd just say don't wait too long to book if you want to get the cabin type you want we booked in june 07 for july 08.we've been told mid ship centre is the best position for reduced noise and movement.
RCI Independence from Southampton would be a good start if you do not like to many kids book outside school holidays they have plenty to do and the entertainment is normally very good,try to get a deal with free parking you park on the dock and the ship is a short walk away?
You are very wise to consider the different offerings because they are aimed at different markets and one man's meat etc etc. Forgetting price as an arbiter, the things to consider are the level of formality, the level of activity you want,the nationality and age of your fellow passengers and for the Med - whether or not you want fly cruise or to travel there across the Bay of Biscay from a UK port. Try and have a ook at the Berlitz book of cruises that describe the lines and give points for each. Their summaries are fairly equivalent to mine and I would classify Cunard and Celebrity as more elegant and best for those that do like dressing for dinner and having classy formal nights. I would classify Fred Olsen and Saga as middle of the road and suited for those wanting a restful time and maybe best for the over 60's plus. Royal Carribbean is more for the young family or those that like a lot of activity on board such as rock climbing, ice skating etc etc. Princess and P&0 are not as formal with Princess being slightly the more up market of the two these days. Since P&O went into US hands they have aimed at the mass market and can best be described as non-remarkable. Island and Ocean are at the informal end and Thompson is old ships and lower prices. Costa are Italian and good for the Eastern Med as it sails from Venice or Savona and if you want to get away from having a predominantly UK and US clientele. Other cruise lines sale from Barcelona or Rome if you want to avoid several days at sea before visiting ports.
Unless any of the above generalisations rings a bell I would advice that you maybe investigate Princess as a possible choice from what you have said. Hope it helps but as I said previously it is very much a case of horses for courses and everyone will inevitably have different views and most importantly, differing requirements.
I'm 35 and hated p&o's acadia a couple of years ago as it was geared up for an older audience and they they just wanted money for this money for that. Went with RCI last year on Navigator and had a great time. Plenty of younger people on the Ship and the kids on board were unnoticable as we went outside of school holidays. Plenty of more mature passengers on board but so much to do you really feel at home.
Do royal caribbean and maybe don't assume because the independance is the biggest and newest it is going to be the best, navigator, brilliance, vogager and even the older legend of the seas are all good and the only thing formal about it is you get to put and suit or tux on or a nice dress if your prefer on 2 nights in 7. If you can't be bothered you don't even have to go to the formal night dinners but we always do as we enjoy the food and company as we've always shared table with some wonderful people especially american couples and families we've met.