I own 6-7 sets of Troy and they work great.

KAC are nice but expensive for something that's a backup to an Aimpoint, Nightforce or Acog that is pretty bullet proof

Steel Magpul ones are good to go

Fixed... I like DD front and Larue rear

Can't speak as to what's best....

But what I like and use are the Magpul Pro's.

Just picked up the rear LR version and going out this afternoon to zero it.

I have used ARMs 40 , PRI and MaTech...they have all done their job...

I just like the design and features of the Pro's.

While I agree KAC makes a very good sight, what do you find makes it the best. I know others have answered the same. So, I’m not singling you out or challenging your particular preference. I’d be interested to hear from anyone in the same boat.

If you like the Pro, you’ll love the LR version. Ultimately, all of my BUIS will eventually get swapped over to Pro LR rears. Gotta wait for those sales

For a long time, I had the perfect rear BUIS sight in mind...

-Low profile
-Solid build quality
-Elevation adjustability
-Dual apertures

Really, not a lot to ask for. Plenty checked 3 of the boxes but none really checked them all. Then someone (Magpul) finally stepped up to the plate. And they knocked it out of the park.

Agee, so far the Magpul Pro LR is pretty nice.
It fits under my LPVO with room to spare, and the same plane aperture is nice.

If it stops raining, I can go zero it.

Maybe I shouldn't have said best, as I haven't tried every BUIS out there, and best is subjective at best.

The KAC sights are low.  Maybe not the lowest, but certainly lower than Troy or MBUS.  They have the ability to correct windage and zero, and the adjustments are easy/repeatable.  They raise/lower more easily than any of the BUIS I've tried.  I actually prefer that they do not lock, as I've never knocked one down, and I would rather need to flip it back up than have it broken off.  I don't think anyone makes a BUIS with better materials/workmanship, and their durability is as good as anyone, and better than most.  Also, they are available.  I bet there are 10 sets for sale on the EE right now, some for the same price or less than comparable sets.

There are BUIS out there that beat KAC on a feature or two, but not the whole package, at least not for me.

Above all of the features, I trust KAC's R&D and manufacturing above any of the other companies making BUIS.

I've never had a set of MBUS Pros, maybe I would like them, but I'm not really a plastic guy, so I doubt if I'd ever truly trust them, even if they have done well in tests.  I've given up on trying to retrain my brain on these kinds of things, and would prefer to roll with what gives me confidence over something that brings doubt.

BCM's sights are a good alternative

Ba Dum Tss

MBUS Pros are all metal construction, so use with confidence.

I like the positive locking of the Pros over the KAC's.  They seem more solid.

Yup, KAC had a problem with the windage on the steel based micros. The spring wasn't strong enough for the detent and when you flipped them up quickly, the windage knob was able to turn and throw your windage off.
The KAC's have a pretty damn weak spring Imo. I've knocked them over multiple times and it's annoying.

Just got back from the range... zeroed the MagPul Pro LR's...   rds and good to go. really like the sight picture. and I was able to get some height back on my Front sight. The PRI rear BUIS I had been using was not calibrated well to the Magpul Pro front... I had to dial the post down quite a bit.

With the LR rear, it was perfect.

shot out to 200meters on paper, good to go.