a9a896a4_SVN_vs_CVS_quick_comparison__SVN
[#] 9 [Compared item] Internal architecture and code. [CVS] CVS is very old system. Initially CVS was written as bunch of scripts around RCS executable. Later this packaged into single executable. But internal structure of code is poor and have lots of historical fixes. Till now there was several attempts to rewrite CVS from scratch, but as it is known without success. We, personally, tried to extract client code to make better integration between plug-in and CVS, but without success. Right now we not think that CVS may grows too much in its functionality. [SVN] 
Subversion authors really spent some time on internal SVN architecture. Still not know how good are some decisions they make. But one is clear, the code is well expandable, and future improvements are coming.
SVN vs CVS quick comparison
SVN