Most of the champions you build titanic on you also build ravenous on. Its generally a preference item and also situational. I always go by my team composition. If my jungler is a utility champion they probably don't have damage so I will go ravenous hydra to even that out. But if my jungler is an assassin I will go with titanic because I will most likely be the one tanking the enemy aggro. It really depends on preference and your team composition on which one is the better choice.
Apologies if that wasn't as specific as you may have hoped but it's how I decide which one is the proper pick for that game.