If you own a 3-stone and a 5-stone for your right hand rings, which do you wear more often? Do you rotate randomly or meaningfully?
Does one yield more compliments than the other, especially when the total carat weight is equivalent?
I have both a 3 stone and a 5 stone. They probably arent exactly what you're looking for as one is rounds and one is fancies.
I think it depends a lot on your finger size if you have a nice small finger. 5 or less, you can get a three stone that takes up your whole finger (a la logansapphire)
But if you have have a larger finger, a 5 stone can take up more room and give you more of the vertical coverage you need. Now, of course, there's lots of ways to break up the same ctw. Say you have 1.8 cts. You could have a 1 ct with 2 40 pointers, 3 60 pointers, or 1.2 ct with 2 30 pointers. All will have a different visual effect. Same with a 5 stone.
Are you in the planning stages of a project? If so I would go to a local jewelry store and try different styles on. I think once you see it on your finger you will know right away what you like better.