Everything else being "equal" i.e. similar loads, motors, ...
Single-phase motors are designed/built "out-of-balance"
(they need to be, otherwise they sit & buzz instead of rotate),
so they wear-out faster, and are generally less-efficient (80%-90%).
3-phase motors involve some additional capital expenditure,
for the additional circuit/phase;
which is paid-back through better economy/efficiency (90%-100%), lower maintenance & operating expenses.