I've got the original on DVD. It is a great show.
Besides the obvious improvement in production values, the big difference is this was directed by Hiroyuki Sanada, a familiar face from a number of American movies (his best movie of his I’ve seen tho is a Japanese production “The Twilight Samurai”).
Mr Sanada, who plays Toranaga in the show, wanted to get it right, Medieval Japan from a Japanese perspective. I dunno Japanese from a hole in the ground but apparently they’re even speaking Medieval Japanese, as alien as Shakespearean English is today.
Looks like they have made some minor changes from the book. I ain’t seen a scene where Blackthorne tries to commit seppuku (hara kiri??). And rather than Toranaga ordering a retainer and his wife to kill their children to test their loyalty (after Toranaga has their children sequestered away so it can’t happen), in this one Toranaga has one of his offending retainers actually kill his infant son before killing himself, so wiping out his line as well, the bereaved widow being made Blackthorne’s consort, forbidden to kill herself until six months have passed.
Yabu steals the show in the vein of Toshiro Mifuni/John Belushi and Buntaro’s character (Mariko’s husband) is a lot more sympathetic than the book/previous series. The Blackthorne/Mariko romance thing, a central them in the book, ain’t given that much emphasis either (other than the fact they like each other, she slept with him when she thought Buntaro was dead, and Buntaro can sense something’s going on but is forbidden to kill Blackthorne.)
Really worth a look.