The disagreement started once we saw all those new Olive Garden commercials doing it. Her point is that nothing is going to taste great with the same thing used twice in a dish. I say differently. Like if you add a good Italian sauce or something and use rigatoni noddles.
I think there’s times where they work better than others and really depends on the dish. If you make a nice vegetable soup with fixed potatoes, and toss in some twirly pasta at the end, then they will work well as a medley and each bring something a little different to the taste and texture. Same with a vegetable curry with potatoes over rice.
If you had potatoes au gratin, and somehow incorporated Mac and cheese, ignoring differences in cook time between the potatoes and pasta, I think you’d feel they were a bit redundant. Not bad tasting, but they aren’t really bringing something that different to the party.
When I think about balanced food I always look to the mix of fats, acids, salts, and sugars with starches providing structure for those flavors. So I would look to mix starches that being a different type of structure to make an interesting dish.