Hi, I've owned them both, but unfortunately not in use side by side nor on the same rack. Equipment was pretty much the same.
The Symposium rollerblocks (somes with a Ultra or Svelte shelf and also fatpadz) used on a Arcici Suspense and the Cerabase's on my Finite elemente master refererence rack.
The Symposium stuff always dramatically lowered the noise floor. All of it, whether the roller blocks, shelfs, footers etc. This is always a good thing in my mind. Better detail, better soundstaging etc. The roller blocks alone seemed to highten detail but loose some warmth. Certain things this is good for system tuning. Used with a Ultra or Svelte shelf, the detail stayed, and things warmed up some (with the noise floor dropping more). All is all, for the money, good, very good. It's addictive to, one you buy into it, you'll keep adding pieces.
The cerapucs I've always used with my master ref finite rack. My, those cerapucs improved EVERYTHING, nothing was a negative. Pretty much a rave. So much so, I bought them for every component I have. Started with one set, now have 5. Plus the cerabases are under my whole rack.
Not sure this helps you out much, but it's my experiences...