I like to use raveners in small squads of 1-2 models. They move and support my hormies in assault. There is alot of competition between raveners and winged warriors. Raveners have 1 more attack, but 1 less str. Raveners can enter difficult terrain, where winged warriors cannot. A 45pt winged warrior has a 4+ save, and a ravener has a 5+ save. Most importantly for me, I can spend only 45 or 90 pts on a small brood, rather than having to spend a minimum of 135 on a brood of winged warriors.
The warriors are great if you're planning on having a unit that can assault independently of any support. A small brood of raveners is key if all you want to do is beef up your gaunts against heavily armored enemies.