  In models with extended scalars and CP violation, resonance searches in
double Higgs final states stand in competition with related searches in top
quark final states as optimal channels for the discovery of beyond the Standard
Model (BSM) physics. This complementarity is particularly relevant for
benchmark scenarios that aim to highlight multi-Higgs production as a standard
candle for the study of BSM phenomena. In this note, we compare interference
effects in $t\bar t$ final states with correlated phenomena in double Higgs
production in the complex singlet and the complex 2-Higgs-Doublet Models. Our
results indicate that the BSM discovery potential in di-Higgs searches can be
underestimated in comparison to $t\bar t $ resonance searches. Top pair final
states are typically suppressed due to destructive signal-background
interference, while $hh$ final states can be enhanced due to signal-signal
interference. For parameter choices where the two heavy Higgs resonances are
well separated in mass, top final states are suppressed relative to the naive
signal expectation, while estimates of the production cross section times
branching ratio remain accurate at the ${\cal{O}}(10\%)$ level for double Higgs
final states.
