Whatever factors impact Infy will impact Cognizant to the same degree. If tech spending recovers, Infy will benefit, and so will Cognizant. Rupee appreciation hits both. US protectionism hits both. Amongst the Indian outsourcing companies, CTSH probably does the best quality of work - if one were to go by the number of IIM grads that chose CTSH over INFY, Wipro or TCS.
Cognizant has grown faster than Infy in the past, and it will grow at least 10% faster than Infy in 2009. I think CTSH will again start trading at a 10%-20% premium to Infy after another 2 quarterly reports. Infy will report next in mid-July, Cognizant in August. So probably by Oct Nov is when CTSH will reassert its premium.