Destiny would have the upper hand at first, but eventually half of all guardians would desert or destroy their ghosts and commit suicide from how monotonous and repetitive their offensive actions get. With essentially no command structure aside from three people who never leave the Tower, faith in the cause would die out and all that's left would be the 'earners' and level 40 elitists. Halo would triumph but would eventually stagnate, due to a lack of originality in new content and the wannabe "Spartan" IV program recruiting nothing but jocks and Sarah Palmer jackoffs. Plus with ONI trying to control everything, what with carrying out an assassination attempt on Dr. Halsey and fueling the Sangheili civil war, the unity forged in the fires of the war against the Covenant would disintegrate and man would eventually destroy itself or end up on the wrong end of the Arbiter's rage.