differences between Modular Separation and Modular Extensions HMVC?

[eluser]ajsie[/eluser]
[quote author="Phil Sturgeon" date="1271166652"]If you are new to CodeIgniter steer clear of HMVC. The cross-calling of modules is not how we do things, and this has always struck me as a bad idea.

Modular Separation is the new PHP 5 only, lightweight replacement for the old (PHP 4 supporting) Modular Extensions.[/quote]

i c, modular separation is yours

i will evaluate both of them, seem to be very good extensions.

why would modular calling be bad? maybe one module is dependent of another? like object composition (relationships between objects).