Personally, when I have cards that can fit into more than one of those columns, such as Utter End, I select the primary reason I want them in the deck
A Food token is a colorless artifact token with "2, T, Sacrifice this artifact: You gain 3 life." Eating, er
Meanwhile, for UW Flash, you have a bunch of value creatures, and while banning any one of Archangel Avacyn, Spell Queller, Selfless Spirit, or Gideon, Ally of Zendikar would hurt the deck, none of those cards really stick out as being too good in a vacuumthey are just very strong when combined together
It draws so many cards, in the color with the best flicker engines like Thassa, Deep-Dwelling and Displacer Kitten
Its Mushrooms and cookies
Elves is really good, but Elves is also cheating on the definition of Tribal