What is the relationship and flow between an Enterprise Architecture Practice and the practice of a PMO?

Question

Depending on whom you speak with, people have different views depending on the structure of the organization.

The first of these views is that when the business has an idea, it engages with the PMO to draft a business case, engage with the appropriate stakeholders, etc. This is generally seen from a cost perspective.

The second of these is that when the business has an idea, it engages with the Enterprise Architecture Office to assess the current state, establish the future state, identify the gaps and then engage with the PMO. This is generally seen from a capability perspective and then cost i.e.

I am however unclear on the benefits and disadvantages of each and when each model is appropriate.

Answer 1

What is it you aim to gain from an answer? What is your role in which any understanding of this matter is relevant?

Whether an individual or an organization follows either perspective (or even yet another) of the ones you described is most likely dependent on one of the following:

Individual interests "Business" usually leads the charge when there is a business stakeholder who has a strong interest in moving an initiative forward and/or wants to have as much control over the outcome as possible).

Even Enterprise Architects can have their own agenda in that they identify new needs from an architectural perspective as a result of some initiative, that are entirely irrelevant for the stakeholder of that initiative. In that case, the original request triggers needs that the budget owner has no stake in themselves, thus requiring EA to make their own requests and trigger new initiatives themselves. These needs usually are related to improving Enterprise Architecture on a structural level, not necessarily related to immediate business benefits.

Organizational culture/practices Requesting requirements via PMO and having that type of entity coordinate any process of shaping a solution seems like something one would only do if this has been prescribed/dictated by organization policies and (most) everyone acepts those.

HTH.