This strikes me as, though I'm unsure as to which technical term applies here, 'liking your theory too much'. 'Tis necessary to calculate the probability of payoff for each of two exclusive options of identical utility in order to rationally process the choice. If Option A of Utilon 100 occurs with 80% probability and Option B also of Utilon 100 occurs with 79.9% probability, Option A is the more rational choice. To recognise the soundness of Vaniver's following statement, one must acknowledge the necessity of calculating risk. [Additionally, if two options are of unequal utility, differences in payoff probabilities become even more salient as the possible disutility of no payoff should lower one's utility estimate of whichever choice has the lower payoff probability (assuming there is one).]*

(They do not always have to be indifferent between bets with identical expected payoffs.)

Honestly the above seems so simple that I very much think I've misunderstood something, in which case please view this as a request for clarification.

[...]* This also seems obvious, but on an intuitive mathematical level, thus I don't have much confidence in it; it fit better up there than down here.