Behavioural interventions that directly influence decision-making are increasingly popular policy tools. Two prominent interventions used are nudges, which promote an optimal choice without restricting options, and boosts, which promote individual capabilities to make more informed choices. Direct comparison is a critical step toward understanding the populations and contexts where they may be most efficient, or potentially complementary toward improving their effectiveness. Two trials in the US and Serbia (N=1,423) tested a series of choices under uncertainty using both nudge and boost interventions. In a replication setting, hypothetical and consequential decisions are used. Findings indicate that disclosure nudges and boosts, unlike social nudges, promote more advantageous financial decisions. Furthermore, the effects of disclosure nudges and boosts generally differ depending on loss and gain framing – boosts promoted more advantageous decisions under gain frames while disclosure nudges did so under loss frames. Finally, boosts were typically more effective for those who initially made suboptimal choices and sociodemographic factors did not mediate the effectiveness of the interventions. These insights provide clarity to highly nuanced, complex patterns across population behaviours in the context of financial choice under uncertainty and considerable implications for the design of interventions for policies that impact population behaviours.