The best perks in Call of Duty: Ghosts are those that give you more damage, help you stay hidden and give you an advantage in contested firefights.
I found that the AK-12 is the best gun in Call of Duty Ghosts. The maps are fairly large so naturally the assault rifles have an advantage over submachine guns. Also, if you are ready for enemies, the AK-12 is very powerful at close range and can easily keep up with submachine guns.
The Chain SAW Light Machine Gun has the fastest fire rate but lowest accuracy, range and damage of the light machine guns. You can only fire it from the hip meaning that at long range it will be unlikely you can hit anything. Because the Chain SAW has low mobility and slow handling you need to stay a bit defensive with it. It is good at holding down a position and can take on multiple enemies at once.
The Ameli Light Machine Gun has the second highest accuracy with the highest damage of all the light machine guns. It has fairly high range but a low fire rate and mobility.
The Ameli is best at medium range but also works well at long range and short range if you are prepared for enemies.