It's a great question Mauro. with Microsoft Project Online is a solid platform, and the lack of updates is indeed a concern.
When it comes to comparing it with OpenProject Enterprise, it really boils down to your primary use case.
If your main goal is project portfolio management, particularly for a large number of complex projects, then from my experience, Microsoft Project Online is generally more robust. It's built for that enterprise-level oversight and reporting.
However, if your focus is more on schedule management for individual projects, OpenProject Enterprise can be a good starting point. It offers strong scheduling features and is quite capable for day-to-day project execution. But, in the long run, and as your projects potentially grow in complexity or interconnectedness, Microsoft Project (even the desktop client) often proves to be more robust for advanced scheduling, resource leveling, and dependency management.
So, for portfolio-level reporting and strategic oversight, I'd lean towards Microsoft Project Online. For day-to-day schedule management, OpenProject is good to start, but Microsoft Project tends to have more muscle for the long haul.
Hope this helps with your evaluation! Francisco