What is golf ball compression and why does anyone care? Its actually very scientific and also the same reason that golf ball manufacturers spend millions of dollars developing new generations of golf balls. It's also why golfers will spend so much money for the best golf ball. So how does it work? And why should you care? Let me stay away from too much scientific stuff (we're done school aren't we?!).
Everyone that has ever played golf has wished they could get just a little more distance out of their shots. Whether their drive or an approach shot I challenge you to show me a golfer that at some point hasn't uttered the words, if only I could hit my [insert club here] just a little farther". Well, in order to get the most distance out of all your shots its important that you're playing with the right ball. So what is the right ball? ITs different for everyone. but in the context of golf ball compression what matters is that everyone should choose a golf ball with a compression that matches their swing speed.
Now for the technical background stuff to start... As a ball is struck, the majority of the power is created by the compression of the ball (i.e. the ball is indented) and the resulting action of the ball springing back into its original shape. This is similar to a ball bounding off the ground. In this case the ball is the ball and the ground is the face of the golf club. If a golfer plays with a ball which is very difficult to compress (higher compression balls - 100, 110, and higher) he/she will not get as much spring action, and therefore distance, out of the ball unless they hit it with enough force to cause the compression of the ball. Because higher compression balls are harder to compress the higher the compression the harder you need to hit the ball to indent it (which will cause it to spring back into form). If you don't hit the ball with enough force to compress it adequately (regardless of the ball compression) it will not travel its maximum distance.
For this reason, balls designed for ladies tend to be easier to compress as their swing speeds tend (generally) to be lower than that of the average male golfer. Lower compression balls (i.e. 60, 70, 80) will compress more easily allowing for maximum spring back into shape and thus maximizing the speed at which the ball leaves the club.
It's important to note that while a high compression ball is more difficult to compress, if a golfer has sufficient swing speed such that they are able cause the face of the club to impact the golf ball with sufficient force to compress the ball adequately the spring (i.e. the bouncing back into it original shape) of a high compression ball is more forceful than that of a lower compression ball. Therefore, compressing lower compression balls the same amount as high compression ball will result in different distances, with the higher compression ball traveling farther. This would be only because of the speed with which the high compression ball bounces back to its original shape as compared to a low compression ball.
One last note, all golf balls (regardless of compression rating) will be easier to compress in warm/hot weather as compared to colder weather. So, if you normally play with a 90 or 100 compression ball you may find that on the hottest days in the middle of summer you can get the benefit of a higher compression ball and hit the ball just a little farther than you normally do. The same is true if its cold out in the spring or fall in which case you may not be able to compress a high compression ball the same that you would in the middle of the summer. You may find that your shots are not going as far as they normally do. You may want to consider using a lower compression ball to compensate for the temperature which might cause the balls to travel farther than you can hit the high compression balls given the circumstances.
Bottom line is that you're going to need to test out various different compressions to figure out what ball reacts best to your swing speed. There's no point in using a high compression ball if you can't compress it sufficiently. Enjoy the longer distance you'll find when you hit the ball that matches your swing speed.