Bev,
We just prefer a villa, we like the space, I know this will sound sad, but here goes - I like to cook, I like to eat when we want to eat, be it at home or out and about, I like to keep the washing up to date, hate bring home cases of washing, also less to take with us. I have always booked villas even when we have been to europe. I always book our own flights/accommodation/car/insurance etc., not necessarily because of cost but I like the choice and I like doing the research.
But I am not one to be blinkered, so I will have a look at a package through a tour operator. We could prob book a holiday through a travel agent and choose a villa? Virgin on line do them, as well as TCD. You might well have a point, do it all through one place and it could indeed work out cheaper.