I'll take a quality scope any day and every day over irons on my big bores.
Why? Am I misunderstanding how you use your big bore? I.e. close range
Everyone will have a different opinion and you need to go with whatever you feel comfortable with and whatever works for you.
Sure, in the purest sense a big bore is for short range and larger animals. For really short range work I’m happy with either but if you wound an animal and it takes off you’re likely better off with a scope. Also when it comes to identifying game that’s obscured by bush or you are hunting in poor light, nothing beats a scope.
A good set of irons you’re comfortable using and a low power fixed or variable scope in Q/D mounts covers all bases IMO.
