I also have to chime in for DI. Works fine, very reliable, standard replacement parts available from countless sources and less expensive.
Of the brands you mentioned I like Daniel Defense. BCM is a great choice too. Like mentioned above you can build/buy a lower receiver and an upper receiver and pin them together for a decent savings (probably $100 or more). You don't get the comprehensive factory warranty though. I did this for my first AR and now doing it again with the incredible sale smartgunner.com is having on Daniel Defense uppers. I will pin it on a S&W lower waiting for it.