If I had to choose a horse in this race I think that I may go with Russia.
US shale drillers are facing a wave of bankruptcies no matter what. There will be massive consolidation / reorganization with most private equity backed companies disappearing. The “buy and flip” model that has been popular over the past 6-8 years is over.
That leaves OPEC vs Russia. Both rely heavily on O&G revenues for government budgets with breakeven most likely higher than the current market price. The difference is that Saudi Arabia in particular needs the revenue for massive social spending and subsidies that keeps the population from uprising against the royal family. It’s no secret that KSA is the epicenter of the Salafi jihadist movement and based on MbS recent string of arrests for “treason”, it looks like plenty of powerful people in the royal family / military / intelligence groups are not happy. Russia, on the other hand, seems to be almost completely united behind Putin. They have also endured far, far worse suffering than whatever low oil prices will bring. They have a pretty good record in wars of attrition.