Re: Magpul MBUS
I have a rear MBUS on my Colt M4. It is designed to be a back up, and that is exactly what I use it for on the M4. To back up the optic.
I have several sets of the Troy BUIS and there is no comparison as far as quality. That said, I do think the MBUS is "good enough". I trust them to do the job, but if it was something I was going to be using constantly, I would spend the money for Troy sights.