Mercy.
I've seen and used a bunch.
This is one of those subjects where you usually get what you pay for.
What I look for specifically, AA or 2032 cell batteries because I have plenty of rechargables for both types.
As for red dots, I won't purchase one that has any less than 11 brightness settings. Having one with only 7 brightness settings tend to wash out in sunlight.
As for the more economical red dots, I like Millett and Bushnell Trophy really well.
I also have Bushnell Holosight AA and N cell that are made by L3 Eotech, but marketed for Bushnell.
I have an Eotech 552 that I like, but other than the NV capability, is functionally no better than the Bushnell AA Holosight, which was also about half the price of the Eotech.
I have used BSA, which I haven't liked. I have tried tasco's which I haven't really liked either.
I have a Bec red dot on my SMG that has always been great. I have actually wondered just how long it would last, but it's been on there for about 4 years and still going, so while I was surprised that it's done as well as it has, but it's been like the energizer bunny and just keeps going.