How do they differ from layers in Photoshop?
Layers in C1 are adjustment layers only and you are still in a parametric editor. The way to localize edits is by drawing masks (analogous to layer masks) for the region where you want the apply the edit. Layers in photoshop can be adjustment layers or bitmap layers, which increase the size of the file.
If Adobe put the effort, they could make the adjustment brushes in LR work like the layers in C1.
What is missing in LR adjustment brushes?
- No way to assign a name or a label
- There is no way to select an adjustment brush that is just below another adjusment brush
- There is only a limited set of adjustments that you can use (HSL panel for instance)