Summon Lesser Demons and Conjure Animals both summon creatures of equal CR (with CA potentially summoning a single CR 2 creature where SLD cannot), however:
- Conjure Animals summons creatures that are friendly, where Summon Lesser Demons does not.
- Conjure Animals' summons will obey your commands, where Summon Lesser Demons' summons will not.
- Conjure Animals can be upgraded by spending spell slots of level 5, 7 and 9, where Summon Lesser Demons is upgraded by spending spell slots of levels 6 and 8, and has no equivalent to CA's final spell slot upgrade.
When given the option to cast either spell, why would someone cast Summon Lesser Demons?