It's a personal preference thing, but for that bike I would go with the 10 or 12.
FWIW, years ago, I got a chance to ride an '01 CR250 with a 14 oz, and you could tell the weight was heavy. My bike at the time was a '99 CRE250 with an eline lighting coil, which acts like a flywheel weight. Riding the bikes back to back, the 14 oz was slower to rev and felt less responsive. IMO a 10 or 12 would have been better.
BTW, if you are doing trail with lots of rocks and roots, you will want to get your forks revalved. I'm sure there are others, but Factory Connection does a good job with old CR forks for the woods.