Although there are many different types of venoms with distinct compositions, I'm inclined to believe that Orochimaru is just as, if not more proficient and knowledgable in poison production as Sasori, and there is a scan (which I'm too lazy to look for right now) where it states that Orochimaru made sure to make him immune to most types of poison, or something similar. Having said that, Sasuke has both the mental and physical reactions necessary to counter Iron Sand, as well as the body/durability in CM2 to withstand it. If I had more time I'd go into detail, but I think Sasuke wins with high difficulty.
Edit: There's also the fact that Orochimaru and Sasori were partnered up in the Akatsuki before the former defected and did many things together, as noted by Sasori himself.