Murali definitely. He only has lesser wickets because he's played fewer matches. But is average is much better.
Unlike Murali, Warne has never performed very well against India.
Plus Murali had to go through hell when his action was questioned (by an Aussie umpire).
@tarey: His action has been cleared by the ICC and everyone has made their peace with it except a certain Aussie umpire (who got kicked out of the elite panel this year).
PS Didn't Shane Warne admit to giving information to a bookie along with Mark Waugh? IMO he should have been penalised just like the other cricketers implicated in match fixing.
PPS As you can see I don't like the Aussies much. Arrogant, racist SOB's. I guess writing all this makes me a little racist too.