personally i prefer when compression is enabled within SSL, although it appears on bodies compression is several percents at best, but, as i mentioned in release notes, zlib within SSL in principle allows selective compression of bodies and headers (so headers would go compressed and bodies - not, thus not wasting processor resources).
the xzver/xhdr header compression commands (added in v2.4 as xzlib option) also acceptable for users who may not wish to use SSL and maybe easier to support on the server side.
accelerator is provider specific custom approach, i think it has something to do with their pricing scheme - giganews is the only provider who charges for SSL separatedly, the xzver would fit that, but it was proposed only recently. accelerator is using selective zlib compression, nothing else there, just the protocol is proprietary, so newsreader cannot know the compressed bandwidth value (thus bandwidth limiting when needed should be set in accelerator, not in the newsreader).
the lack of zlib support you can see on the server icon, the lock (which designates SSL) has grey color, if SSL zlib is enabled it has yellow color (winzip icon color
), when grey, it is rather small deceleration on bodies because of SSL protocol overhead.