I'm assuming this page didn't help you out:
The above link (Backup.CompressionOption) only refers to the current database backup. This server-wide option can be found within SMO's Configuration properties. What you're looking for is DefaultBackupCompression.
Hope that helps! I know it's a little late, but it may help others who stumble upon your question from Google.
Chrissy, wow! You have really jumped in there and are contributing a lot of good content. But these are some really old threads and I have no idea is the original posters are still around.
As Chrissy said, her answers might help others. Great contributions, Chrissy!
I'm so glad that you've joined Bob and other "power" members who provide amazing answers and share their knowledge.