I have done some work on the dendritic spine development field. Please have a look at the following review article that should give you a starting point with some key and classic references in it. This review compares developmental changes in dendritic spines between the motoneurons and Purkinje/pyramidal neurons.
regards,
Refik
Article Emerging Roles of Filopodia and Dendritic Spines in Motoneur...