petrova just hasn't performed at the slams like the others in the poll. kuznetsova has an RG final and a slam win at the us open. dementieva has 2 slam finals, myskina has won a slam. petrova's best at a slam is a SF. she's had a great run lately, and i think she's probably the best russian on clay (even though she lost 1st round at RG this year).
if you go on slams, kuznetsova has equalled the best performance of petrova and myskina at AO (QF) and bettered dementieva's best. at RG she's done better than petrova, equalled dementieva and come a match win short of myskina. at wimbledon she's equalled myskina and petrova and bettered dementieva and at the us open she's done better than all of them by winning in 2004. so on the big stage which generally is where the top players like to shine, kuznetsova has performed better than any of the other 3 on this poll overall.
Go the aussies! stosur!!!
and good luck russians: dementieva, safina, kirilenko, sharapova, kuznetsova, bovina, zvonareva, dushevina.
also good luck to: azarenka, lucic, sprem, vakulenko, vaidisova, safarova, ivanovic, groenefeld, mirza, krajicek, kvitkova, larcher de brito, lisicki.