Further the tendency is to eat one far more potatoes than fruit. Also a banana has a GI of 52, vs 85 for a baked potato vs pure Glucose 100( http://nutritiondata.self.com/topics/glycemic-index) other sites have different numbers but always place a potato significantly higher.
I have seen one study that concluded that boiled white potato was the most filling of all the foods tested. I don't recall whether bananas were included.
Equal-calorie portions of specific foods were given to volunteers, who were then allowed to consume until sated from a buffet. Those who ate boiled whole potato first ate fewer calories from the buffet than any other "appetizer". Noteworthy was the fact that french fries and baked potato--made from the same stuff--scored abysmally by this measure, almost the worst of all foods.
Boiling, chilling, and reheating your potato to plate temperate may even enhance this effect through the process of starch retrogradation.
Bananas are typically eaten uncooked. Potatoes are barely ever eaten raw. And it would also appear that the method of preparation has an effect.
It would certainly be possible to test the experiment result at home with a food diary, to see if adding one food in particular to your diet causes you to eat more or less in total than is usual for you.