mobile

Hey guys, so in my country they sell the D821 N5 but I was eager to get it first so I ordered it from the US, and got the D820. My dad and I are on the same carrier, and in the same area. He has the D821 and I got the D820. For some reason his reception is better and he has significantly better battery life. He's not rooted or anything, and I AM. I used every trick in the book to improve battery life and I still get a max of 2 30 SOT while his average is 4.
Does that has anything to do with the models of the phone? Maybe the D821 is sold here for a reason and that'ss why my reception is worse? If I were to enable the LTE bands, would it do anything although I'm not using LTE?