Big Beyond belief has alot more options and in more depth, covers diet, multiple programs from 4x week to 6x week/twice a day.
Titan is more of leaflet than book, not very big at all. Only one program in it, but brutally hard, brutaly hard!!
I got my best results from BBB, and is better value for money content wise.
Titan has an interesting approach, and I often left the gym seeing stars. when I did Titan on was on a cutting cycle so potentially could have gained more if ate more calories
I would buy both again if I had to, but if was just getting one would I get BBB.