I either have, or have had, every rifle mentioned except for an AR10. Of the ones I currently own, I like my M14 the best. Hands down the best iron sights of the lot.
However, if I was looking for the one rifle that I could shoot with either iron sights or scoped, I would pick up an AR10. I don't know enough about them to say which one is the best one to get, but the ease of installing different sighting systems as well as being able to change uppers in seconds, makes it the the most versatile. I don't know the OP's budget, but I think a decent AR10 can be put together for somewhere between $1000-1500.