I gotta say, I really like Ashtons' philosophy:


From their FAQ:
Why only one head? Where's the variety?
Our view on this is simple. We've designed the best driver we possibly can and until we can make something better, we won't. We don't understand the practice of introducing multiple heads that all do the same basic thing. If you want to hit the ball longer and straighter than you ever have, you've come to the right place.