from the research i've done:
Home Defense: short, plain barrel: I think the 870 comes in 18 or 18.5" lengths
Clay shooting: long vent rib: 26 and 28 are readily available for the 870
Hunting: Ask the killers
I'd also look at the Mossberg 500, as its the Ford to the 870s Chevy.
If buying new, you can get combos around this time of year, with 2 barrels, most common is rifled for hunting, and longer VR barrel. Or buy whichever you want, and the alternate barrels separately but it'll cost more. Lots of used available for both.