"We have a large house."
Translation:Meillä on suuri talo.
This is just my thinking, and I don't know if there's any difference actually.
Iso is for when something is physically big and suuri for when something feels big. Compare English big and large. Iso is concrete and suuri more abstract.
If a man is iso, then is either muscular or overweight. If a man is suuri, then he has "a big heart", or he can just be big.
Iso leaves the feeling that something is described as is to be big. Suuri conveys that the speaker was also impressed by the bigness.
Feelings are most often suuria. Having isoja feelings would be pretty weird.