Front-up: I'll never buy that scope, not because it's not good (it probably is), but because it's way out of the hobby league - and I know that and while I understand that humans, once triggered, just love to discuss about "things in another galaxy" I also know that all the matters, facts, and "facts" discussed here are of no, none, nada practical concern to (certainly not only) me.
If this was a discussion in real life I'd probably jokingly complain to the R&S guy "what? Only 500 Mpts/ch? Come back again once you have a scope with >= 50 Gpts/ch!"
What I see here basically is just a MXO4.2. Some more of this, some more of that, a faster processor, yada,yada, but at the end of the day I just see a scope that makes better use of R&S' ASIC. That's nothing to sneeze at, but it also is not like we finally could fly to the next star, like "a new era".
And I'm amazed yet again how happily (almost) everyone accepts the usual BS. Example: If an ADC does 12 bits that doesn't mean that you actually get 12 bits because at the end of the day measuring, as opposed to guesstimating, means ENOB, and that is more like 9 bits - if you are very lucky and using a low sampling rate. Yes, averaging helps if some conditions are met, e.g. the thing you measure is repetitive. But still 12 bits is the limits.
Beyond that one finds oneself in BS territory, or in polite marketing lingo in math/statistics territory. Allow me to introduce you the 5 cats in my neighborhood. I know their precise size: 34.567 cm. OK, granted, not even a single one of them actually is 34.567 cm long, one, a kitten, easily and cozily fits in my hand while it's (likely) father is well over 50 cm long. Of bloody course we all like precision, accuracy, and high resolution, but let us not forget what it's all about: measuring that is, obtaining quantitative information about something physical!
See also: the miracle of 6.5, 7.5, and 8.5 multimeters with single or even 2 digit ppM measurement certainty (and, of bloody course, hardly any of them actually is beyond x.3 digits. In fact, some of the "very best of the best" actually are very close to x.0 digits ...).
I'll end with (surprise!) kudos to R&S because AFAIK they stopped at 5 3/4 digits. I may be wrong but my guess is that some of their engineers back then said "Nope. We don't take part in the BS-your-customers game!".
Btw. does R&S also sell the MXO5 in six-packs? I'm asking because buying a scope for 60 k€ + VAT isn't worth to leave the house *g