Definitely Blu-Ray. Microsoft doesn't have experience creating new data storage formats. Also HD-DVD was there only chance against Sony's BRay.

Get good with the Battle Rifle, and I recommend the needler for easy kills because it is devastating. An SMG/Plasma Rifle combo is good for close range since Covenant weapons are good for lowering shields, while human weapons are best at killing dudes with zero shields. Getting used to the Assault Rifle never hurts as well. You really can't stick to 1 weapon for you are boned if you respawn.