I use Matech BUIS. Mainly because that is what I use on my issue weapons. They are relatively cheap, new on ebay, for about $50. Great quality and durability.
another thing about the Matech BUIS is they are designed to have the same windage and range elevation controls as an M16 or M4 with the carry handle upper. I honestly don't know what would make a BUIS better than any other after you zero it, except for the durability factor for maintaining zero after being dropped or something.
Now that I think about it, I do NOT like the Magpul ones. When you look through the rear site, the area outside your site picture is obstructed a good bit by the bulk of the plastic housing.
I have the Troy on my primary, it's a very solid unit. They all perform about the same though, and I wouldn't have a problem with a Magpul on my rifle either. If you're rocking a quality optic they truly are BACKUP iron sights and will most likely spend their life folded and forgotten about.
I have yankee hill on one and ARMS40l on another. both co-witness fine. I prefer the ARMS. I am switching over to aimpoints after 5+ years with eotechs.