If you cannot decide on any of the destinations so far, why not indulge in them all. To circumnavigate the world on a luxury cruise ship, spending the whole winter in sunny climes, is the dream of many.
Several of the most modern ships are too big to take on the 100 day voyage, especially as it is not possible for vessels in excess of 100, 000 GRT to transit the Panama Canal. However those that are larger do sometimes offer itineraries that transit the world without use of the canal and it is worth bearing in mind that the canal is also currently being expanded to allow larger vessels to enter.
It is easily possible to cruise round the world for less than £10,000, although most passengers prefer to add some extra luxury by investing in more spacious accommodation and a balcony.
Larger cities such as Sydney, Dubai, San Francisco and Rio de Janeiro usually see ships staying over for one or two nights. Often these ports are used as the start or finish of a cruise between 'legs' of a world voyage and there are plenty of opportunities to join a world voyage at different points.
A world cruise is not every person's idea of a perfect holiday but those who have invested in this three month experience of lavish lifestyle and new horizons rarely regret doing so.