cato censor who's right durant or wheelocks?

I have a question. After every speech Cato the Elder said I think carthage must be destroyed. Wheelock’s and two of my professors have told me that the quote is Carthago Delende est and this is mirroed in Wheelock’s. Will Durant in Caesar and Christ gives the quote as Ceterum censeo delendam esse Carthaginem. My question is Who’s right and why? would someone provide me with a gamatical/historical explanation?