If you are trying to learn how to ride off road, you might think about 13 47 or even 12 47 , however you will be stuck at about 80 kms per hour on the pavement and change your gearing when going on an adventure ride.
Start with rides like this http://www.dualsportbc.com/forums/showthread.php?14162-Deroche-Nicomen-Nob and hone your skills and mods in a test mode with a little slower paced type of ride but still challenges available just not the whole ride. Sounds like some of the Squamish rides might fit the bill also for getting to the balance of bike and terrain, before you change your commuter bike into the bike of all evilI just installed a 14 tooth on the front for a 14/44 combo. I seem to have a lot of chain slack though. Going on 2-1/2 years and 15000km. Does that seem like the time has come to replace the chain? Oh wait. I just found my answer in a Clymer manual. Apparently for 21 pins, the service measurement is 319mm. Mine is 321mm. I guess I'm shopping tomorrow. Hello Holeshot?