IUI or IVF?

Devon • She loved three things - a good joke, a glass of wine, & a handsome man.
I've read plenty on both procedures, but I'm still a bit confused. I completely understand each of the procedures, but what I'm having trouble understanding is what makes couples decide on one or the other? I would just like as much background knowledge as possible before going to a clinic! 
Can you do <a href="https://glowing.com/glow-fertility-program">IUI</a> with stored sperm? 
Is <a href="https://glowing.com/glow-fertility-program">IVF</a> a "last resort" deal? 
What is a deciding factor on which procedure to go with?