One of the reasons I have the Siglent on the radar is that apparently it can decode the entire memory - but that depends where you read. I saw Dave's hour long on the siglent sds1202x and was pretty impressed, I've since looked at the siglent sds1202x-e but it seems to be inferior to the one Dave tested, they seem to be totally different beasts - I could be wrong of course.
What they have in common is very similar base UI but each has different features.
Dave has looked at both but at the time he had X-E it was a pre-production 100 MHz model that was removed from the lineup to be replaced with only a 200 MHz version.
The X is a nice DSO, bit bigger display and 50
inputs but the X-E has more grunt and the 4 ch X-E will have further added functionality due to the better X-E processor.
Please be aware that when Dave does most of his vids, products are fresh to the market and with subsequent firmware releases they change and even features can be added. Unfortunately this makes his vids somewhat out of date after only a few months so I think what he tries to do is look at an overview of the unit rather than full examination of all features.
How scope memory is managed when decoding is entirely manufacturer dependant, whether it be from memory or by use of zoom when you can have a few seconds in the unzoomed window and and ms in the zoomed one.
Trigger settings and Search functionality then allows you to find something 'not right' rather than have to pan through all the decoded data.
As others has said, the power of any DSO is in the Trigger suite available, it can be free in some scopes and you need to pay additional for it in others.