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.