There’s an interesting article on the Magic: the Gathering website by Mark Rosewater, lead designer of the game. Talking about the upcoming set of cards, he discusses the importance of balancing game mechanics that make the game feel cool (form) and mechanics that make the game play well (function):
If all the mechanics sit in the middle straddling function and form, the set will suffer. It will neither play as tight nor feel as evocative as it needs to. Both extremes play an important role in design and thus each needs to have cards at its beck and call. This means that designers have to understand the role that each mechanic fills.
You can read the whole thing here.