The divine-name example shows that rhetoric works through meaningful lexical selection. An overt name brings its own semantic content, while a pronoun derives reference from context. The referent may be the same while the effect differs.
ExpressionPotential effect
Pronoun: عليهEconomical reference to someone already known
Overt name: على اللهRecalls the divine name and strengthens the exhortation to trust
This does not make pronouns intrinsically weak. Pronouns can be highly eloquent when cohesion, brevity or flow is the point. The test remains fitness to context.