J7 is in lower mid range price. n a7 is a upper mid range premium phone. there is alot price differences in between j7 and a7.
If you want just a big phone n good battery life then go for j7. n if you wan a premium and good looking phone with high screen quality and powerful then go for a7 but battery life will be 2 hours less then j7.
j7 lack many functions. I had use j7 for almost a month and found that it lack many functions so I switch to a7. but I must say I like j7 batery life .