NONE, I'd say scope it, especially with a study QD mount. Trash scopes are easy to trash, but good scopes are now reliable up to and including the 50 BMG round. The scope is a better system for DG in all but the most experienced hands, especially for a moving target. PH's prefer irons because they use their rifles at very short ranges, if at all. Last time I went to Africa with both a scoped and an iron sighted big bore for DG, the PH looked at the iron sighted one and said, in the words of James Thoroughgood, "let's leave that one alone!" I never shot it. Also, remember that a DG rifle that is capable of being scoped is worth far more than a similar rifle with irons only, double rifles excepted, of course.