HX1000i will be better since it has better internals. I've heard some pretty terrible things about the RM series. Hence the reason why I went with a Seasonic X-850 as opposed to a corsair RM850
BTW! What are your reasons for getting a 1000w PSU? Do you need it? Or is it just personal preference? I got my Seasonic X-850 850w PSU for only $76. Just to give you an idea of how much you're spending on a PSU.