We would need the exact models or links would be best to compare apples to apples . I've noticed DD to have more upgrades on there rifles come as standard free float rail better stock nice trigger etc . that brings there price up and with out knowing what models you are comparing to each other it's hard to say what's a good deal for the money .
All the manufacturers you just mentioned make great rifles and you will not go wrong with any of them . I will say again that I would not spend 1k on a standard AR with standard M4 stock handgaurds and trigger . You can find those for $900 and less all day long .
Why do I carry a 45 ? because they don't make a 46