I don't have a ton of experience with pumps, but I have a decent amount.
I have never seen problems with the 870Ps except for things like old ammo coming apart in the tube (which is a nasty mess). But, that is also a sign that folks weren't doing much in the way of training or maintenance. What I HAVE seen problems with is folks with 870 Express-types. But, virtually all of those problems were people trying to do piecemeal upgrades like, "I bought a better bolt" but not knowing enough about the action to make sure it was fitted properly.
Because of experiences with a Remington 572, one area in the trigger group that I have always been wary of is the "action bar lock" - I broke a couple in my .22 as a kid, but have never seen signs of the same part failing in the infinitely more robust trigger group of the 870.
In terms of the other brands - the 870's of the early 90s seemed far more reliable to me than the WInchester 1200s of the same era, but that is based on pretty anecdotal information at best. I don't have anything I would consider real data. In the modern era, I think an 870P or a Benelli SuperNova Tactical would be the choice to make for a pump - but the Mossberg 590 is no slouch either.
-shooter
In a recent case a shooting buddy of mine who I was shooting wobble trap with. His 870 hung up after he talked me into giving it a try - causing me to miss a bird, and THEN he says, "it must be the new bolt not cycling". I replied, "what was wrong with the old one?"
I have this crazy belief about solving actual problems...
-shooter
I was making a joke at my own expense. Having bought an NOS 870 Express with the MIM extractor, I had it replaced with a current-production non-MIM unit... and then flew all the way across country to a big ol' 3 gun match without, you know, function checking the extractor to see if it needed any burrs dressed off.
I have seen several fairly pricey "custom" 870's all suffer the same type of failure, broken ejectors like this one.
This caused a problem with extracting spent shells from the chamber. The edge of the brass rim would catch on the broken part. I haven't held the same opinion of the 870 since.
Surprisingly 870 have been giving more and more trouble lately. At a 3 gun I hosted last September a new shooter with a new 870 had his extractor fly off the gun on the 2 round fired. A few years back I saw several 870's go down at a match I hosted that had over 40 required slug shots. (I will never do that again in a match people hated me for it)
Here is an 870 I had rebuilt (was a old gun I got for $100 bucks) giving me troubles. Something got caught under the shell release arms that hold rounds in the magazine tube. I had to finish the stage single shot.
http://www.youtube.com/watch?v=4e9_Eg0pigo
This, IMHO, is why I'm really not able to recommend 870's.
That and if you're a lefty, you're SOL for the safety.
Oh and don't snag your hand in the feeding gate.
Oh and you'll have to take your hand off the grip to cycle a round in the chamber.
I know I've heard good things but, I'd take a Mossberg 500 or 590 (if you really want a metal trigger guard and bayonet lug) over a Remington 870.
Just my $.02.
Ditto, even though the safety doesn't work so well with a pistol-grip stock. I'll take it over a cross-block button safety any day.
That's true of most every off the shelf shotgun not built for competition. My Weatherby tried to bite off a fingernail earlier thus week, really need to get that welded up.Oh and don't snag your hand in the feeding gate.