Holosun. Sounds crazy. Been shooting RMR's extensively for the past 3 years. Between the 3 that I have, each one probably saw at least 10-15k apiece on the gun they were mounted on. I absolutely hate seeing folks spend hard earned money on sub-par gear.
I won't name brands or models, but there are a lot of options that are not duty grade, and didn't think that anything could top the RMR in this market. Snagged a 507 type 1 to see what the hype was all about and loved it so much, I swapped that one out with a v2 just recently. The 508 is the same thing made with titanium instead of aluminum. The tint is much less on the 507, the reticle is sharper, and the window is just slightly larger. It's enough to make tracking the dot through recoil a little easier. The only thing I think the RMR does better at this point is its auto-adjust is marginally better. The durability aspect is important too, and at this rate - anything that makes it through Cowan's testing is encouraging. I love the fact they share the same footprint, so you're able to try both. Definitely not dumping my RMR's at this point, but I just had my annual battery swap-out party for my pistols and I left the 507 on my primary carry gun. Even if they were priced exactly the same I'd choose the 507.
What I do want to emphasize is this - it's not a life shattering difference between the two. I find one marginally better than the other but would be well served with either. Very curious to see what Trijicon does for their Type 3.