Onion vs. N-Layered Architecture

Though it is very old question, but would like to add something.

Onion Vs Layered

This article explains it clearly why layered is not preferable but if you have implemented IOC correctly, it ain't gonna make any difference.

Adding facades are really the first step in building an onion architecture out of an n-layered architecture. So, yes, you can get many of the benefits right away.

Testing is still problematic as you need to invert the dependency control. Controlling what has the facade is pointing to needs to move to the consumer, not the provider. This allows that consumer to swap things out for testing, or to change implementations without the provider having to know about it.

I'm sharing the same opinion as yours, We're planning to kick off a new project and one of my coworkers suggested the onion architecture, but after documenting a bit about it I was a little bit confused, because (for me!) the fact that each client layer must depend only on the abstraction of the used layer is a matter of best practice that must always be in mind whatever architecture we're planning to use, DI is a "Principle" not an architecture so I couldn't realize how just using the N-Layered architecture with "good OO Principles" make it a new architecture?

In this way we'll end by hundreds of new architectures just by combining all OO Principals and Go4 patterns to the Entreprise Application Architectures.