I suppose then we just need to come up with what "entirely different effects" means. Standard way of handling illusions are whether you are changing or creating, how large/detailed the change or creation is, how much substance it has, how long it lasts, and if changing whether it is yourself (or parts of your self) or others (or parts of others). So, in our case, you'd have one illusion spell for "changing a small body part of myself for a minute with no substance behind it" that you could use to make your hand look like a claw or your head look like a cobra's hood.
Do not thing abstract.
If the same concrete term applies to both effects, it can be the same spell. "soldiers" is such a term, leaving the details of weapons and banner to casting time. But you'd do quite some semantic gymnastics to find a common term that encompasses both soldiers, horses and a bridge.
