Van Dijk will become the most expensive defender in history once his move from Southampton officially goes through on January 1, surpassing the £54m Manchester City paid for Kyle Walker during the summer.
However, Warnock - who revealed that he had the chance to sign Van Dijk for just £6m while at Crystal Palace - insists that his current centre-back Bamba is more accomplished than the Dutchman.
"Van Dijk's got better attributes on the ball but I don't think he's a better defender than Sol Bamba. I think Van Dijk is more confident on the ball and easier on the eye but I don't think he's better defensively," he told reporters.
"When I was at Palace, the centre half I was looking at was van Dijk and I suggested we buy him for £6m.
"At the time the chief scout said he wasn't quick enough, he was playing in the Scottish League and he didn't see him stepping up to the level we were looking for. I hope he's watching this morning that chief scout, £75m? It made me smile when I saw that."
Cardiff currently sit third in the Championship table, only outside the automatic promotion places on goal difference.