Well cypress, I have many. But your question answers itself for me - they are all "second favourites." Limited by work (college holidays) and money, I can only spend four weeks a year in Corfu, and Arillas provides me with more than four weeks worth of "first favourite" activity. So I never stay anywhere else. That doesn't mean I know nothing of other centres in Corfu, and indeed I have visited some them. Fortunately, my better half feels exactly the same, so PhilnJen are Arillas folk, together.
Arillas is unique.
In a very few years I will be able to spend most of the year there, with a very contented wife who is looking forward to it as much as me. Then we will spend some time in other parts, such as the Diapontian islands of Mathraki, Ericousa and Othoni, but will probably do a lot of Sidari, out of peak season, as well. It is a very different place in October.
Phil