The rapid advance in gravitational wave detectors has spurred renewed interest in the two-body problem in general relativity. Two perturbative approaches based on quantum field theory have emerged, one based on scattering amplitudes and the other based on worldlines. We argue that the two approaches are equivalent at an intimate level. By systematic algebraic manipulations through the Schwinger parametrization, the loop integrand in the Kosower-Maybe-O'Connell formalism based on wavepacket scattering becomes identical to the counterpart in the worldline QFT formalism of Mogull et al., as shown explicitly for a simple scalar model as well as electrodynamics at two loops. This makes manifest the cancellations of superclassical divergences and exhibits the emergence of the worldline picture including the classical causality flow.