I did some shopping for a RDS this year so I'm hoping I can help.
For a non-magnified red dot, I'd check out an Eotech (I know it's technically not a RDS but it serves the same role) as well as the Aimpoint. Compared to the Aimpoint, Eotechs have a larger "window" and some people prefer the reticle. Traditional Eotech reticles have a 1 MOA dot (in practice, 1 MOA vs. 2 MOA makes little difference for a non-magnified optic) surrounded by a 65 MOA ring which supposedly speeds up target acquisition. Some of the newer Eotechs have extra 1 MOA dots to account for bullet drop at longer ranges. FWIW, Eotechs and Aimpoints are both standard issue for the U.S. military and I think the Eotech 553 was recently ordered by CF so they're both practically indestructible.
The biggest difference between the two (as mentioned in some earlier posts) is Eotech battery life is measured in hundreds of hours (my EXPS3-0 comes in at around 600 hours) while Aimpoints are measured in tens of thousands of hours (50,000 hours for the Micro). If aesthetics and weight matter, the Micro is tiny and a lot of people think it looks more streamlined. The Eotech's a lot blockier but weight/size-wise I don't find the EXPS to be too bad but it's definitely not in the same class as the Micro. As far as brightness, on full intensity you can point either into the sun and not have the dot wash out (unlike your eyes). One last point - Eotechs have integral mounts but not all Aimpoints will (you may have to buy the ring and mount separately). The Micro has an integral mount but I don't think it's capable of co-witnessing with standard height iron sights out of the box so you may still have to buy a mount if you still want to use your BUIS (any Eotech with the QD mount should co-witness, not sure about models without QD mounts). This might be something you have to consider if you're on a budget.
Elcan's official stats say minimum 300 hours.
When the CF bought the EOTech, they were not yet owned by L3. I had one on my first tour in Afghanistan and it worked okay, but all four other ones we had went down for various reasons - two needed new battery compartments, two had the magic just leave. On my second tour my EOTech died within a month and I finished the tour with a Comp M4, no issues, no battery change. We use RDS for most courses now and the EOTech's come loose, the Comp M4 and M3 and PRO have torque knobs and stay on and keep zero.
EOTech claims to have improved this with the current production, but I have not used any of those yet.
The US army, most recently, bought only Aimpoint. The last contract was for over 500K sights. One million in service with US army alone.
EOTechs zero tends to drift with temperature as the laser refracts differently - the collimating hologram is supposed to stop this in theory, but we found differently over the last ten years particularly in the fall with morning frost and warm afternoons.
The EO reticle is nice - it helps avoid cant. A small level on the rail also helps with this on an Aimpoint.
The window makes no difference - they are both collimator sights and can be fired with both eyes open or as occluded eye gunsights. Both will make yucky reticles if you have astigmatism bit shooters have reported to me that the EOTech is worse.
Did a test with 6 of each. Fire a group, partner screws with dials, fire a group, measure and adjust by those measurements. All the Aimpoints were bang on, the EOtechs had a large variance. EOTech adjustments are exposed and have alight detent. Aimpoint adjustments are covered and have a positive detent.
Last year the Aimpoint rep did that test with a micro on and SA80. The he took it off and flung it over his shoulder onto a concrete pad and then put it back on and fired a group on zero. It's on my shotgun now. Same battery, small dent on one corner.
Micro has risers available to co-witnes. Bottom third or centre. Comp and PRO have the same. Pretty sure you will need one anyway unless you have no cheeks. OST has a few aftermarket ones I think.
Both EOtech and Aimpoint have magnifiers. I prefer the twist off Aimpoint mount and the EOTech magnifier is better.
