I am not interested in Destiny at all but I will be getting Titanfall day one

I think it will depend on how the hype is playing out 4 months from now on the power difference between the XB1 and PS4. If every game comes out and looks similar between the PS4/XB1, then I would say Titanfall will be bigger. If the PS4 is already having a distinct visual advantage, then Destiny will be bigger as people naturally migrate to the PS4 for the Power.

Titanfall will be bigger on consoles and Destiny will be bigger on PC. Titanfall speaks to the heart of the twitch loving console fanatic.

I also think Bungie/Halo fans are some of the most loyal fans in gaming.

No doubt most Halo fans will also be attracted to Destiny.

COD has a lot of casual fans. Even Activision admits most COD buyers aren't really gamers. So I don't think Titanfall will get that huge immediate following that COD has, while Destiny will immediately get most Halo fans.

Right, but it's just surviving off of the Bungie name for now. It looks fun/cool, but Titanfall is going to be advertised as another attempt for EA to challenge CoD's sales numbers with the Respawn dev team. 

As a Halo fan, I rather Destiny do well, but MMO's have a hard time surviving lately. Bringing the FPS crowd to an MMO...it'll be an interesting way of showing how dedicated Bungie fans are to their dev team.

Destiny is more of a complete package.

Halo fans will be drawn to the sci-fi environment and story. 

Destiny is also trying something innovative by doing an online-campaign. Something few other console games (if any) have successfully pulled off. 

Destiny is going to be bigger I reckon, could be the biggest new IP next gen.

Bungie are by far the better developer, but so far Destinylands looks meh. Titanfall seems to be the far more hyped up title for now.

Knowing Activision, Destiny will be marketed to high heavens, and then rammed down our throats every 1-2 years. The MMO aspect of it seems cool though. Unfortunately, the last publisher to try an MMOFPS was Sony, and we all know how that turned out. Destiny won't flop, but it probably won't take COD's place as Activision's flagship franchise. On a side note, in the Bungie-Activision deal, Activision is supposed to publish four Destiny games. 

As for Titanfall, EA will inevitably market this as YET ANOTHER attempt to take down Call of Duty. It didn't happen with Bulletstorm, Bad Company 2, or Medal of Honor, so it won't happen here. The lack of a real campaign will hurt the game, and it's not releasing on PlayStation systems. 

With that said, Destiny will be bigger. Unless Titanfall is a runaway hit, I see it fading into obscurity in 5 years, after a sequel. 

Destiny, because its launching on more platforms and it has the Activision/Call of Duty marketing machine behind it.