Excellent post! I already made two runners based off your templates, so thank you very much.
Binding spirits seems only worth it if you plan on Invoking (metamagic) them or making them an Ally Spirit. Please correct me if you disagree.
Binding's pretty strong. 1 spirit buddy is really good, a small army of spirit buddies is better. Binding also gives you access to the fairly handy Aid Sorcery service*. If you do want to go down the binding route, you'll want to be a charisma mage so you can have lots of bound spirits.
Binding's nuyen cost ultimately doesn't matter much if you're a pure mage. You'll rapidly be looking into useful money sinks. Binding's main drawback is the drain. A force 6 spirit rolls 12 dice so you're likely taking 8 boxes of damage (likely physical). But it could spike to 12. However since binding is 100% downtime, all that matters is that you don't get KOed or killed while binding. If you're still standing, you can get medkitted and/or nap for a few days before your health matters.
You do want a extremely good drain roll (12+ dice) before you go down the binding route. Since having a high drain roll is extremely useful for a mage in general, this isn't as much of a cost.
You can easily live as a mage without binding. However, it's respectable choice to be a binder. It's more useful than banishing at least.
*- It does need to be at a force equal to the spell's force. So it's not especially handy for combat spells since you'll need to have a bound force 8 spirit for your force 8 stunbolt. Due to hits being capped by force as well, mystic adepts do the best here since they'll have smaller dice pools than full mages. But a +5 to health or detection can be handy to make sure you cap out on hits.