Smart has *way* more value. AB is currently a better player, but really not by much; he's a much better shooter, but his other offensive skills are below average, while Smart has started to show some ability as a slasher, as a PnR playmaker, and as a distributor. Smart is also an outstanding rebounder on both ends. It's fair to assume that within a year, Smart will be much better than AB at every offensive skill except shooting, making him a net better offensive player even if he doesn't become a competent shooter. Defensively, AB is an unreal on-ball defender, but Smart has surpassed him overall with his versatility and off-ball defense. AB is on a good contract, but he's still getting paid a lot more than Smart, and he'll be a UFA whereas Smart will be restricted when he hits FA.
Also, I would not be happy if we traded either for Okafor. I think that he will always be a bad NBA player who gets overrated and overpaid. He is one of the worst defensive big men I have ever seen.