and more from Dave at Blue Line -- an interesting comparison of sights:
"Just to update this thread and bring it back to the top, here is more information on sights and on the 870 Express models.
The 870 Express is designed as a 'price-point' gun; it gives good value for the dollar and gets people into the solid design of the 870 without too much money. The downside is the finish is a bit rough and the black oxide coating is not as durable.
The 870 Police is made on a different line and is made to much higher standards with the finish and some of the internal parts.
The 870 Marine Magnum is still one of the best pump shotguns in the world and I would sooner have an 870 Marine Magnum over any two other shotguns combined (aside from a Benelli M4, of course.)
It is always up to the buyer what is most important for their purposes. My training shotguns go through hundreds of thousands of rounds and I would not use an 870 Express for this. But for others, it gets you the solid design for less money.
The 870 Express Tactical models are designed for those who want some 'tacticool' accessories, and the looks of the 870 Police without having to pay 870 Police prices. BUT I would not trust an 870 Express Tactical with my life right out of the factory. I have struggled and struggled but to this day I have not found a solution to the problem of a shell slowing slightly as it reaches the joint between the mag extension and the magazine tube. 99.9% of all the shotgun shooters out there would never approach the speed of shooting at which this becomes a problem, but when one shoots and pumps as fast as some of my students can, this becomes an issue.
I would therefore NOT use an 870 Express Tactical for serious purposes unless the mag extension is replaced with a shorter spring and a Remington end cap. I may be stupid but I would easily trade off two rounds of magazine capacity for 100% reliability (plus, learning how to properly speedload a shotgun, of course.)
Given a choice, I would spend the extra money on an 870 Police or an 870 Marine Magnum, and replace the stock with the Hogue overmoulded stock for a simple, light and reliable shotgun.
As for sights, I have been torture-testing a variety of electronic sights for an upcoming article, and I acquired both the Aimpoint Micro H1 and Micro T1. They are fantastic sights and I am really liking their size and handling characteristics when mounted on serious shotguns.
The Aimpoint Micro sight has the advantages of a battery-life measured in years, and an easily-found 2032 button cell that powers it. One mounts it, sights it in and leaves it on; only replacing the battery every four or five years.
The Insight MRDS doesn't have quite the battery life of the Aimpoint, but it will also last years when left on constantly. It takes a far-less readily available 1632 button cell (PLEASE Insight - change this design!) but it does have the unique feature of an ambient light sensor that adjusts the dot brightness to actual light conditions. (It works great!)
The EOTech is larger and heavier than the previous two mini-red dot sights, but it is very tough. (The opening shot in my article is the EOTech being driven over by a truck.) The lighted reticle gives a slightly more accurate sight picture at the expense of fractions of a second in speed. It also shows if the weapon is canted when firing, which can affect point-of-aim. Battery life is measured in hundreds of hours instead of years, but it is not designed to be left on all the time. (In fact, it will turn itself off after a certain number of hours if not being used.) It can be turned on VERY rapidly though, so this isn't as big an issue as it may first seem. (The target reticle on the EOTech consists of multiple tiny dots, so it take lots more battery power.)
Just to illustrate what my sights go through ... I was doing a combat shotgun demo the other day with a hostage and target scenario, with the heads edge-to-edge at 7 meters. First, I took off the Insight sight I was using, threw it as hard as I could directly onto the concrete and watched it bounce off a steel sidewall. I then mounted it back up again and rapidly fired two rounds of 00-buck into the head of the target without putting a single pellet near the 'hostage.' How's that for confidence in your sights?"