I think in America Playstation will win again similar fashion as the PS4, where it will be a narrow victory. Some people believe Xbox with win in America but based off of what I am seeing on data and small sample polls most Americans seem to be favoring the PS5 over the Xbox SX, I know it's just a small sample size, but usually those polls could give a good indicator of what the casual market is thinking as a whole. It's gonna be close but I expect PS5 to win again in NA.
In Europe Playstation will blow Xbox out the water in terms of sales, maybe slightly closer since Xbox is now starting the gen off with the price advantage but there simply isn't enough marketing from Microsoft in Europe to put much of a noticeable dent to the market share in Europe.
Japan should be slightly better this time for the Xbox since the Xbox Series S is a small console which appeals more towards Japanese consumers who tend to live in smaller areas and maybe the emergence of Xcloud grow Xbox's market share in Japan, where Japanese consumers are more into portable gaming and where internet speeds are fast enough for cloud gaming. Maybe if Microsoft somehow manages to make Xcloud big in Japan it could threaten Playstation's market share in Japan and I wouldn't put it past Microsoft to make Xcloud big over there. However, as of now it seems unlikely. So while I do believe Xbox SX will do better in Japan, it still should be no where close to Playstation. But I wouldn't say Japan matters that much anymore for either company since the home console market is for the most part virtually dead in Japan and Japan's sales won't make much of an affect to the worldwide sales total of either console.
In the rest of the world, Playstation 5 again should have a pretty sizable lead over Xbox SSX. Mainly due to Sony's marketing all across other regions while Microsoft doesn't market much outside of English-speaking countries and I doesn't seems to care about beating Sony in sales figures anymore to change that. However, if what people in the thread above me say is true that Xbox games are cheaper in the ROW, maybe Xbox could regain smoe market sure in those regions. However, I still think Playstation will win pretty easily.
So worldwide, I agree that this gen in terms of sales will be very similar to the last. I expect both Playstation and Xbox to sell even more this gen but market share to remain very similar.