I am thinking of running a campaign for Dark Heresy 1e for my players, and I was curious to know what the general opinion is on the 2 pre-written campaigns, Apostasy Gambit and Haarlock's Legacy. I'll probably end up reading them both anyway but I would like the opinion of people with more experience than myself.

Haarlock's Legacy is the only one I would actually call new character-friendly, much less new player friendly. Apostasy Gambit you practically need established characters and players to really make it work. Either way, if you want to do an introductory game introducing people to Dark Heresy 1e, dig up Shattered Hope and Edge of Darkness. Lead that into Illumination from the CRB and then diverge to where suits your fancy.