I think SNY doesn't win as big as you suggest in the first scenario, since it seems the majority have been selecting PS5 over DE. With a $299 XBSS, assuming it has an optical drive, I think consumers will see a $499 PS5 and XBSX more so as the next step. That's a pretty big gap, and should lead to even higher XBSS sales.
In the second scenario, it should be a much closer race. Why buy XBSS for $299, when you could have XBSX for just $100 more? Way more performance and no compromises with the optical drive. Though how many will think why buy XBSX, when you could have PS5 for just $100 more? No that many I'd guess, based on the paper specs and marketing.
If by the majority, you are referring to posts on forums and tech types on youtube? Then that will give you a very skewed data set to draw your conclusions from. As those represent the vocal minority.
With regard to the mass market, I think it will surprise how many people are willing to forego a disc drive if it means they save $100. And digital game sales representing more than 50% of game sales these days is indicative of this trend.
That second scenario I gave isn't something I believe is even possible. XSX can't be just $100 more than the XSS. Impossible. But that's the only way I see sony being in any sort of trouble.
The only real "ideal" scenario I truly see (unless sny fucks something up) is scenario one, where the XSS cost $299-$329, the PS5DE cost $399-$449 and the XSX/PS5 cost $499. But in that situation, the real fight is going to be between the PS5DE vs XSS (which is likely also going to be all digital). And in that case, the PS5 DE offers the far better value. Besides, I don't see a $70-$100 price difference between the XSS and PS5DE being enough to shift sales in favor of the XSS.
The biggest issue I see for the XSS is that it will look, and seem (even down to its packaging) like the "poor mans XSX". And that's because the only thing missing in the cheaper PS5 is a disc drive, wheres the XSS is butchered compared to the XSX.
Funny enough, when rumors of Lockhart started making the rounds and before sony revealed the DE PS5, I actually sad that the worst thing that could happen for MS is if sony somehow priced the PS5 to be in the middle of the two MS SKUs. Granted I didn't anticipate a digital PS5, but that's exactly what sony seems to be doing anyway.