Business is much more straight forward, and I would say it’s more scoring than economics. However, it doesn’t mean that economics cannot be scoring. A 7 in economics HL would be valued more than a 7 in BM HL.
Also, it’s not about how much you write. Writing two sides for a 10 mark answer should be enough but you need to practice solving past paper questions in economics, regularly to get into the habit because you’re gonna be short on time.
So yeah, if you’re looking for a subject where you have to work very little, go for BM. You will have to work for the 7, but not as much as in economics.
And as far as IAs are concerned, I take both on HL and I didn’t really have an issue getting that 7 in both.