I am sure there are threads out there like you said that discuss this in detail.
This is one of those "genre sub-label" quandaries. Much like in metal, people will argue 'til the cows come home over these things.
Generally speaking, Delta blues is as much about style as it is region. The "Delta" that is mentioned is the Mississippi delta. (
Mississippi Delta Wiki link)
The musical style is usually distinguished by an emphasis on rhythm, bottleneck slide guitar, and harmonica. Other blues styles grew out of this like "Chicago" and "Detroit" styles, that in my opinion tend to be a bit more refined.
These are all loose labels though in my opinion. Guys like Elmore James and Skip James are often considered Delta blues players, but were not from the Delta.
As with other genres of music, when we try to start pigeon holing these guys into categories, things can get confusing.
I will list a few of my fave (not inclusive) "Delta" performers anyways..
Elmore James
Muddy Waters
Sonny Boy Williamson
Pinetop Perkins
Mississippi John Hurt
R.L. Burnside
John Lee Hooker
Howlin Wolf
Robert Johnson
Son House
Skip James
Junior Kimbrough
I like my blues more raw and gritty, some prefer their's refined and technically superior.
I think the main thing to remember is that "blues is blues". Hope all of that didn't confuse you further.