Of the two, I would prefer BOOM! I feel like BOOM! has a better track record as a publisher of comics than Titan. That's just a gut feeling, though.
Here's the thing. Titan has almost no history as a comics publisher. They have a book division that occasionally publishes comics (Lenore
, the Torchwood
comic), and now they're starting up a separate Titan Comics. The book division's comics had no sort of regular schedule, and that doesn't instill me with confidence that Titan Comics will be any better.
But, Titan has two advantages that BOOM! does not. They already have a Doctor Who
license for merchandise, so they're familiar with the BBC approval proces. And they're in the same time zone as the BBC headquarters instead of being nine or ten hours behind like IDW was (and BOOM! would be).