If one barrel length could do it all everyone would a shotgun with one barrel that perfect length. It's very quick and easy to change barrels on any pump shotgun. I recommend a Mossberg 500 combo. It has a 24" rifled barrel and a 28" accu choke barrel. You can find the Mossberg combo about anywhere. You can even order one from Walmart. The 500 combos run around $350 plus tax.
I own both a 500A (12 ga) and a 500C (20 ga) Mossberg 500 combo. They both are very accurate. I made the 500A into a dedicated slug gun. It has a 4x scope on it and a single point sling. I did away with the williams sights that came on the rifled barrel so I could use a low profile scope mount.
If you can't afford a 500 combo here is a great deal on a stevens combo. They are out of stock right now but this is an item Buds carries regularly. Two of my friends have bought one recently.
odds are youll never have a home invasion encounter. but odds are, youll enjoy your gun on a range more. go with a 26" bbl or better and go have fun with it, then switch it back when youre finished for the day.
Try a 22-24 inch barrel you do this by buying a 26" and cutting it down. Have it threaded for Remington chokes and use a tritium bead not ghost rings. For clays and game use a turkey choke every thing else a full choke works quite nice. No extra barrels needed. Also but a three gun mag extender for extra rounds. ;-)