Emirates so far has been the best airline I have used for traveling with firearms. Last year I was met by an Emirates representative at the Alaska Airlines gate, accompanied to baggage and assisted with getting rifles rechecked onto Emirates. The representative then came on board before departure to confirm for me that my bags had been loaded onto the aircraft.
On the way back a representative was waiting to assist me in Seattle when I cleared customs and made sure firearms arrived and I got on my way to Alaska Airlines for the final leg home. It felt like VIP service both ways! The experience I had with Emirates was so far superior to Delta in every way, and for much less money, I will likely not fly Delta again unless I have to.
I would just book with Emirates and not worry about it. They seemed much more worried about getting me and my guns where I was going, and treating me in a very respectful and professional manner, than anything else.