There are so many delicious varieties available at the moment and each has its own type: sweet, acid, firm, juicy, crispy, pink or red fleshed, there is a lot to choose from!
Obviously, choosing a type of apple also depends of what use you want to make of it: is it just for eating on its own or adding to a delicious dessert? Some can serve both purposes but some others might only be delicious as cooking apples for example.
My favourite for baking is of the Cox variety. I love its flavour and how easy it is to cook with. It is sweet enough that I never need to add sugar to it, especially when I make apple puree (also known as applesauce) to include in some of my favourite desserts: apple tart and apple shortcrust turnovers.