Quick answer : Army A. But your facts are flawed.
We had that discussion before. The distance is almost the same on both side (alliance rezzing at spgy>shgy, horde rezzing at cave>bgy). The only real imbalance is horde can rez 20 in cave while alliance can only rez 10 at spgy. However, it’s very rare more than 10 people are trying to rez at any gy at any time. If so, the group will probably lose anyway when occupying another graveyard. Far from a game breaker in my opinion.