Nvidia cards are superior for distributed computing in general. Take F@h protein folding, or space research such as SETI for example;
Nvidia cards fetch 4-10x more performance than a comparable ATI/AMD card.
Also most supercomputers in the world use Nvidia cards or ASICs.
http://www.top500.org/
You named the 2 projects where the ATI client is a fail: Folding and SETI. Folding ATI client is so much fail, and the staff state this too, it's a known fact it's not optimized. As for SETI, well, same apply, it use mostly the CPU for the computations.
Let's speak about Milkyway, Collatz Conjecture, DNETC (and Moo! Wrapper), where both the nvidia and ati client are fully optimized. ATI simply kickass nvidia in all these projects, especially in Milkyway where double precision is used.