By far, Batista.
Orton, last year, was the most popular he's ever been, and he did nothing for business.
Batista brought a 40% increase to Raw revenue as soon as he won the Royal Rumble in 2005 and WWE hasn't looked back since. Actually, if you look at the numbers, he was the biggest star the company had until mid-2006, even while on Smackdown for most of that duration. I won't go into the success he brought Smackdown as a brand and the fact that he was the biggest international star WWE had until 2008.
Orton isn't in Batista's league when it comes to starpower.
The only thing he has going for him is the advantage that Batista decided to leave when he could have headlined for another two years and cemented his legacy further. That, and Orton still has around 10 years to add to his legacy. But even with that, his highest high will never reach Batista's. That much I guarantee you.
Batista is, was and always will be the bigger star.