What is the key difference between مُوسَىٰ and دَلْوٌ for case marking?

Noun Case Classes: Type 1 (Ḍamma, Fatḥa, Kasra)

• Both are always indeclinable
• Mūsā has estimated case; dalw shows its ending
• Dalw can never be genitive
• Mūsā is always a particle