Well, imagine it is a CTF or INF, or whatever team game it is. Is the team score more important or your individual score more important?
And, if you haven't realized, the minigun's killing ability is actually increased. Faster firing rate. It still retains the same bullet push (due to its new firing rate and bullet speed) while all other guns have weaker bullet push. And if you calculate it, the Damage per Second is now higher. And higher bullet speed and lower bink, which means I can shoot over a slightly longer range.