Several years into using Pro, I still find myself getting these two mixed up.
Aside from both having the same briefcase with a pie chart (?) icon, the one on the right has a window behind it, which to me should be the View icon since it opens a window view of roughly the same aspect ratio, but it's actually the pane button, which is confusing since panes are typically much taller than wide. The briefcase alone, which I think of as being more portable (i.e. pane), is actually the view.
I wonder if these icons could be revised to be more easily differentiable? I understand they're somewhat replicating the ArcMap and ArcCatalog icons, but this wasn't really a problem there since ArcCatalog is a separate application (as it should be!).