Titanfall has no story, so there's nothing to keep me coming back, really.
Destiny, being another Bungie creation, will have a rich and deep story, and this time, they will retain the IP rights to the franchise, which means that the story won't suffer at the hands of hacks like Karen Travesty or Greg Bear.
For long-term (if the end game is good) Destiny. Titanfall will be that game I'll on a day to day but if the end game on Destiny is good then Ill play that more also Halo 5 if 343i go's back to the play style like Halo 2 or 3 Ill make time for all of them.
Titanfall will be a good placeholder. I need to get used to ADS in a competitor setting so it will be a good training game for me. Plus it looks badass.