You can't compare ray tracing and FWI since ray tracing is a "forward modeling" tool while "FWI" is an inversion process based on a full wavefield modeling (FWM) engine.

Ray tracing is based on the approximate high-frequency solution of the elastodynamic equation. RT is generally used to obtain wave path and/or travel time between a source and a receiver in a velocity model. It's widely used for P-/S-wave travel time tomography and it is generally limited to single scattering.

FWM allows to obtain the full wavefield (P, Sv, Sh, Rayleigh, Love etc), for all type of wave at each point of the velocity model and receiver position and is not limited to single-scattering or a single type of wave.

This is why travel time tomography results consist in map of velocity variations while FWI results are velocity models in terms of absolute values. However, TT tomography does not need accurate initial model and TT tomography results are generally used as starting models for FWI.