Having just played this for a couple of hours i have to say i much prefer it over Reach.
Story wise i've only done one mission, so i can't say much on that regard, but just did one Spartan Ops mission, and i feel like i'm gonna put plenty of hours into that, and i can't remember if they had it in Reach, but i like how you can get Exp via local multiplayer as well as Solo SO mission.