Mir, I don't have a document prepared but as an experienced user/consultant in both products I can provide some high-level feedback:
CA SCM is more intuitive to use,
CA SCM requires less training and admin resource,
CA SCM performs better,
CA SCM does, effectively, achieve the equivalent of both ClearCase & ClearQuest (one product, not two), and
CA SCM can be implemented 'Agentlessly'.
These are just a few off the top of my head. The obvious bias is towards CA SCM but that is purely my opinion, from experience.
It may be worth also looking at Rational Team Concert which, I believe, is the product from IBM that is superceding ClearCase/Quest.