Just pointing out advantages of the S6000
Much larger display
double the polyphony
The Z8 has other advantages so they should be pointed out, but
Everyone needs to know what they prefer or need.
I would for example NEVER buy an S5000/Z4. The remotes make the S6000
and Z8 massively useful in a studio situation (but the S6k remote is huge which helps). No reason to lose that to save a few pounds.
Then again most people seem to just want to load libraries rather than create them, which is where I come from (and I route any of my gear through my desk and into the S6000) so as you say if loading existing 24 bit files is your thing, the Z series is the only choice. If creating original sounds is your thing, I don't see 24 bit as an advantage.
In creating sounds I find the S6k OS and display great for that.
Personal choice. Neither is better but each has advantages over the other.
(oh and as a sampler addict, I am very happy with what I have. The S6k sits amongst many other classy samplers (S-770, EIII, Fairlights) as would a Z8 I am sure)