The Cunard Mauritania, Lusitania, and Aquitania represented a significant commitment to using turbine engines, but the White Star Olympic, Titanic, and Britannic used a mix of reciprocating engines to drive their two main propellers, with the smaller center-line screw being turbine driven.
Wikipedia notes that White Star had found the configuration to be more efficient than all-turbine or all-reciprocating designs, but I was hoping for more information on what criteria and research each company was basing their decision on, as well as how the two disparate propulsion systems were received at the time. I.e. was one considered more sensible/unusual by the public or engineering community at the time?
My (admittedly limited) understanding is that since Lusitania and Mauretania were built under contract with the British Admiralty they had access to various resources that WSL did not. Amongst those resources were people with the latest and most comprehensive understanding of steam-powered technology, namely Parsons Marine Steam Turbine Company. WSL's knowledge wasn't quite as advanced so they used a proven design of their own.
As conjecture, it would make sense for the White Star Line to effectively bow out of the race for the Blue Riband under these circumstances and how Mauretania was able to retain the prize for decades.