I'm no gospel on the subject...BUT...
I was always told that the factory rating is what you want to stick with as it was designed and tested to function perfectly with the caliber of the gun and the standard spec loads that go with it. If you go up, you risk the gun not cycling properly and causing feed or ejection issues, if you go down the spring can't do it's job to properly buffer and protect the gun from the recoil, and can cause damage from the repeated 'slamming'.
Only time you mess with the weight of your recoil springs is if you're changing the load you're shooting...if you're shooting hotter loads than standard, you'd want a heavier spring to protect the gun. Lighter loads, a lighter spring so that it cycles properly.
Of course, changing out your factory 14# spring for a Wolff 14# would be a great idea as part of routine gun maintenance.
Again, I'm no prophet on the subject but this is the knowledge my grandfather passed down to me about it. Others may have different views.