I don't disagree with Milo, because everyone should have a spare ball, or at least find a house ball that fits in a pinch. Every bowler leaves 10-pins and a "straight" ball will make your life much easier.
If you want to hook the ball, you are more likely to develop bad habits trying to hook a spare ball, so to speak. It depends on what you want first.
For your first performance ball, though, I stand by my original post.