My problem is that I keep unlocking new weapons and I really don't understand a great way to compare the guns. I understand that if I start with a new weapon I need to spend a lot of time to unlock the good unlocks for that weapon, but there must be some general consensus as to some top guns and attachments.
Weapon comparison charts:
Each site has forums with more discussions on the subject.
There really isn't a "best gun", it depends on your play style, your class and in the end what you are comfortable playing with.