SPHINX+ is actually slower (which does not matter much as firmware signatures generation or verification are not time critical) but it is the most conservative

SPHINX+ is actually slower (which does not matter much as firmware signatures generation or verification are not time critical) but it is the most conservative choice available (avoids only relying on the security of lattices for signatures), which is very valuable for firmware that cannot be easily updated if a security issue arises with lattice-based signatures. It also offers the smallest public key size, which may help for devices with limited storage.