Only the 55 inches of older models of X7000E are VA , 55 inches of X7000F is IPS .
That's pretty much the difference , you are paying extra for the Android OS. But Sony 's TV Android OS is prone to crashes and sluggishness , some people prefer it because it offers more apps . They have also removed some of the trivial features such as the support of 5GHz Wifi on the XF70 .
Because it is the better TV among your options for dimmer rooms ,  any difference you see in the shop might as well be the result of different settings .
The Samsung TVs  will look more washed out when viewed from the sides because it has narrow viewing angles ( which is the flaw of VA Panel based TV) . But it is a little better for watching HDR content thanks to the coverage of wider color space.
That's the thing with 4K TVs ,  if you don't sit close enough to the screen , any picture improvement to 4k is not very visible to our eyes ,  hence not worth paying extra for the 4K upgrades .
It's difficult to say if TV A or TV B has better upscaling , because any difference might be caused by different sharpness settings.
Most big brands TV runs a very identical upscaling algorithm , but certain brands like Samsung's TV tend to overscan the screen causing the overall picture to look a bit more blurry .
Once these extra processing effects are turned off , the upscaling quality should look pretty much the same unless you are running test patterns and using magnifier to spot the difference.

The primary difference between the two is still the HDR performance . The 6800x supports a wider color space than LE580X but this colors improvement is only visible in HDR TV shows , movies and games .  If you don't watch / play HDR content , might as well stick with the 580x.