The AH is not a directly important number. A larger number does imply a "stronger" battery, in that it will take longer to run down, but under normal circumstances you should not be running your battery down.
As long as it is a 12v battery designed for motorcycle use, it won't harm your Versys regardless of the AH rating.
Normally the battery only supplies power to start the engine. After that, the alternator provides all the electricity for the bike, including recharging the battery. If you left the key turned ON but the engine not running, the battery would eventually run down. The 10AH battery would take a little bit longer to run down than a 9AH battery.
The higher AH number may be better under a few circumstances. Primarily if you live in a very cold climate. That doesn't seem likely for you in India! Other circumstances would be unusual, like many engine starts for very short trips (package delivery) so that the battery can't recharge fully each time the engine is running, or if you're powering something from the battery when the engine isn't running.
A reputable brand of battery at 9AH won't hurt your Versys and should work fine for you.