@roger,
They're (granny smiths) good for pies, specifically because they're tart and crisp - they don't turn into mush when cooked like some other apples do.
It's hard for me to say what apple I prefer because any apple that's ripe - is an apple I like.
Same with canteloupe, peaches, plums, oranges - I think when fruit is good - it's nature's perfect food.