Spool your reel according to what you are trying to catch. Most people bring multiple reels with different lines to catch whatever is biting.
When fishing for sharks we would use a much heavier line with 10' of steel cable on the end to keep the shark from biting through the line. But then just for goofs we set up the same rig and pulled in 200lb sharks on 20lb line too.
More important than line strength is that you always adjust your drag to let out line before the line reaches it's breaking point. I had a buddy catch a 80lb tuna on 10lb line. It took him awhile but he landed it.
It is possible to catch just about anything on light line with the right technique, enough time and enough energy.
Braided line is nice because it stretches more before breaking. It is also more tolerant to nicking and is less likely to break from it.