One of the big differentiators I see between Nexus and SAFe is the number of advanced sprints planned. In SAFe, the work for the Next 2 Program increments is always being refined. When a PI is planned, there are 5 two week iterations for everyone to review and agree on. This helps a lot with knowing where you are going and resolving known dependencies.
How does Nexus track and resolve dependencies if you are only planning sprint by sprint?
Regards,
Thom