But there is such a thing as BEST FOR YOU.
Only you can decide that.
I like Pump Action because they do have an edge over Semi-Auto's as far as their reliability is concerned. 18" barrels are plenty enough for self defense, and the shorter a gun is the easier it is to manuver in confined areas. Capacity is not such a big issue for home protection. Matters of course would be different if you were a Law Enforcement Officer though. For home 4-6 rounds is plenty and since most pump action shotguns already come with that sort of capacity you are good with whatever you choose. I have always preferred Remington 870's. I have also owned a Mossberg 500, but have gone back to the 870 since.
The rest is up to you. While pistol grips are readily available, a shoulder stock will offer you more control, and since the gun won't be carried folding stocks are more for looks than function in a home defense gun.
**On a side note** While some people feel that a flashlight is a tactical liability (making you very visable to the bad guy) I feel a flashlight is the accessory that makes the most sense on a home shotgun. After all, you will probably need to use the weapon in dark conditions and it is ery important to be able to identify your targets.
What you as a home owner need to do is figure out if a shotgun is an asset or a liability for YOUR home. Home Invasions by armed badguys isn't as common as some people make it out to be, but they do happen. You need to weigh out the pro's and con's before commiting to have a shotgun as home defense. Bad guys do sometimes assault people with their own weapons if the chance arises. Train hard until you know your weapon inside and out & take the nessesary precautions so it can't be easily turned on you and you will be set. Good luck.