You can't go wrong. I owned a 590, was issued an 870, was an armorer and took care of my 870 and those of other officers. The 870s came through the armory for PM, repair etc. once a year. They were most always dry, uncleaned after range sessions, and sometimes rusty due to water leaking into trunks where they were kept, etc. But except for very rare occasion, they continued to function properly.
I preferred the 590 to the 870, and would likely still have it had I not traded it on a new Remington 11-87 Police model some years ago. Good as the 590 was, I don't regret trading for the 11-87. The 11-87 has been pump gun reliable, i.e., never malfunctioned or required repair.
BTW, reference mention of "cruiser ready" for shotguns. Our local department carried shotguns cruiser ready, safety off, for many years. At some point a few years ago, it was decided, by the chief I guess, that cruiser ready would now include having the safety on. I have to admit that the first shoot I attended with the new "safety on" rule in place, caused me some momentary discombobulation when the trigger of an 870 would not pull. I was not issued an 870 at the time, and the gun was a misc. 870 to be picked up from a barrel, and used in a stage meant to simulate a potential real World situation, and attendant stress. It did simulate real world stress when the trigger did not pull immediately as expected:brickwall: