Just think about it.
1. All his base abilities.
2. Edo Tensei - Hashirama, Minato, Tobirama, Hiruzen and potentially more other strong shinobi.
3. Hashirama cells and DNA.
4. DSM.
5. Shin's body to take over whenever he wants to - that gives him Mangekyou Sharingan + an ability to add other shinobi DNA with no risk of rejection.
6. Perfect Clones also with DSM, Hashi cells and MS.
7. Immortality.
Orochimaru solos.
1. All his base abilities.
2. Edo Tensei - Hashirama, Minato, Tobirama, Hiruzen and potentially more other strong shinobi.
3. Hashirama cells and DNA.
4. DSM.
5. Shin's body to take over whenever he wants to - that gives him Mangekyou Sharingan + an ability to add other shinobi DNA with no risk of rejection.
6. Perfect Clones also with DSM, Hashi cells and MS.
7. Immortality.
Orochimaru solos.