Good optics beat good irons everytime. The military has tested this enough to prove that soldiers hit much more often, at all ranges, under all conditions, with some type of optic on their rifle than with irons. If you buy quality they are proving to be just as reliable.
I think dots have their place, but to me the most useful optics are the small 1-4X scopes used on many of the AR's. They are quicker to pick up the target at any range and make shots in low light much easier because you can see the target better when on low powers. At the higher magnification they aid long range precision. They also cost less than a quality dot sight.
That said, I'd not want an AR that didn't also have iron sights as backup. And I'd learn how to use them. So you might be better off for now to stay with the irons. After you shoot a while longer you can make a better informed decision as to what will be better for you.