It's useful to start out on a 9x9 board when you're still wrapping your head around how to figure out if a group is alive or dead and the most efficient ways to make life in the corner, etc. But being good on a 9x9 doesn't actually teach you a lot about how to play on a 19x19, because there's just not enough space to really have an opening and mid game develop.
Learning how to give the computer a challenge on an even game on 9x9 won't make you better at 19x19; if you understand the rules, the very basic fundamentals of good shape, and you know how to fight in the corner, you've pretty much exhausted the usefulness of 9x9 and should move on.
Learning how to give the computer a challenge on an even game on 9x9 won't make you better at 19x19; if you understand the rules, the very basic fundamentals of good shape, and you know how to fight in the corner, you've pretty much exhausted the usefulness of 9x9 and should move on.