What is the most fundamental distinction between ḥasan li-dhātihi and ḥasan li-ghayrihi?

Innovation, Defective Retention, Ikhtilāṭ and Ḥasan li-Ghayrihi

• The former is acceptable on its own route; the latter through outside corroboration
• The former never reaches the Prophet
• The latter is necessarily mursal
• The former always has a one-person chain