Plaster lights are a superior alternative to ceramic lights.  They have several advantages:

1. Ceramic lights cannot be moulded to the same level of accuracy and definition.
This means edges are not as crisp and sharp and often look rounded.  This lack of fine edge definition is quite noticeable up close.

2. Ceramic lights are difficult to hand finish. 
We hand sand all of our plaster lights to a silky smooth finish.  Ceramics have a very hard surface, which makes them very difficult to hand sand.  Ultimately this means they are left with the same finish as when the leave the mould, which can be rough and uneven.

3. Plaster is pure white.
We use a specially formulated plaster, which is completely pure white.  Ceramic lights are more often closer to beige in colour.

4. Plaster can be painted with a superior finish.
Plaster is the same material as ordinary walls, so it can take paint finish with ordinary emulsion and a simple PVA solution.  When opting for a ceramic light, it is often necessary to obtain specialist paint and primers to get a satisfactory finish.  Matching this specialist paint colour to you wall paint an often be tricky.