Well it depends on your reel and how you will be fishing. If using a spinning reel a lighter line is better for line cap. and casting distance. Bait casters work fine with lighter lines or heavier lines, they normally have more line cap. for the heavier line. As for heavier lines for bigger fish isnt needed, you just have to play bigger fish longer with lighter line. In a snaggier area though heavy line will help stop breaking off fish. Thats how i see it at least. Hope this helps a little