Gaussian 16 Revision C.01 ((better)) -

“It was both,” she said. “The revision gave us clearer signals; our parameters let us hear them. But the molecule had the structure all along. We only needed a quieter room and a better ear.”

: Significant improvements were made to parallel performance on systems with large numbers of processors. gaussian 16 revision c.01

If you want the primary source, the official Gaussian 16 Revision C.01 Release Notes (hosted on gaussian.com) are the best technical read, but for a "human" read, searching for "Gaussian 16 vs ORCA benchmark" or "G16 GPU performance" on computational chemistry blogs yields the most lively discussions. “It was both,” she said

Mick Philpott’s Blog (and similar computational chemistry blogs) Topic: Comparing Gaussian 16 C.01 to ORCA 5.0 We only needed a quieter room and a better ear

Gaussian 16, Revision C.01, M. J. Frisch, et al., Gaussian, Inc., Wallingford CT, 2019.