Thanks, it's on my kindle as well (haven't finished it yet though).

As I see it, Culadasa is better suited both for general audience and for those more scientifically inclined - that's why it seems to be ideal fit for HNers. It also seems to be much more ambitious, systematic work (it's his opus magnum). Probably Shaila's books target more advanced meditators - that's not to say Culadasa is just for beginners.