Iggy has more value. I am huge GW fan. I think he is on the cusp of LBJ and Granger level. He can't shoot the 3 as well as either, and his points won't ever be 25-30 a game, but I think he will have just as good DEF stats (if not better) and will have better rebounds.
Iggy is probably worth more in fantasy, but I think GW will produce close to the same. Outperforming him in assists and def stats, but less in asts and points (3pts)