Aside from the obvious program length difference, the 16 week program allows for a “fuller progression” of the lifts, whereas the 8 week program is more of a “training snapshot” (Bryce’s words). Practically speaking, there’s more exercise variation in the 16 week program. If you can afford it, run the 16 week program. If you need to prep for a competition in 8 weeks, then the 8 week program is a better choice. You can also try out Calgary Barbell’s training methods with the 8 week program, which is less of a commitment than the 16 week program.