Bricks is more focused on project management. Though it connects with BIM ecosystem (BCF import, Autodesk 360, Revit plugin), it does not have a 3D viewer. It has a roadmap view and Kanban board that are really useful to plan a project more globally.
BIM sync come in handy for BIM coordination. It focuses on a 3D viewer that can show the 3D model in 3/4 of the screen on which you can add contextually some issues in its 3D context.
Bricks and BIM sync can work together thanks to the BCF format. Bricks can import BCF of issues created with BIM sync or NavisWork.