I own both 870s and 500/590s, and like both styles. If I could only have one, it would be the 870, based on personal preferences...
I prefer the trigger-finger release (with jumbo-head safety) of the 870 over the thumb release - can maintain firing grip with 870 while releasing safety. This is actually a 'learning' for me, having grown up on 500s, and thinking my thumb was faster...
I like the 'smoothness' of my Wingmaster-based HD, and even my 870 Express equals the 590 - both are what I consider 'gritty'.
I also prefer the steel receiver of the 870, giving me more finish options across my armory.
Finally, I think that the 870 has a wider range of accessories available for it.
I'm slowing purging the 590s, and finding bargains on 870s. I'm focusing on one SOP for HD, Hunting and target shooting.
Try both, if you can, if not, get the 870 - you won't be disappointed.
(sorry Dave, only have 2 870s right now, but I do have 6 shotguns, total, does that count?
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Best regards,