The Blu-ray sets have both remastered and original.
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Here is a review from Amazon I was checking out. I was wanting DVD only, mainly for my grandfather, and thought this was interesting
IF YOU WANT TO SEE THE OLD VERSIONS-- as seen on network and in syndication from the 1960s to the early 2000s with the original (Matt Jefferies) special effects and space shots, and original opening credits, you want the set that comes in the RETRO EGG boxes (colored in the colors of the uniforms: mustard yellow, sky blue, and red). These are the versions that long time fans remember. The original footage was cleaned up (a first round of "remastering" years ago) but kept intact. The 1960s special effects, which were state of the art at the time, are intact. In the classic exterior stock shots, the Enterprise is blue-gray. Depending on the shot, the nacelles of the ship (the "exhaust pipes") have either the bulb or vents. The opening credits are the originals: the Enterprise---with the vent nacelles---heads for the right side of the planet, then shifts to the left. The music is orchestral only for the first season episodes, with the woman's worldess vocal for the second and third seasons.
IF YOU WANT INDIVIDUAL EPISODES OF THE OLD VERSIONS-- look for the versions sold in 2-episode cases. The (ugly) packages of these feature photos of the cast members on the covers, with a Star Trek in a florid funky type going vertically up the front of the boxes. Type in the name of the episode you want in the search window. Only the old versions of the episodes are sold separately this way.
For those who can accept nothing less than the original episodes as they were, stick to the above.
IF YOU WANT THE NEW REMASTERED VERSIONS WITH NEW CGI EFFECTS--- you want the set that is packaged in the RECTANGULAR BOXES WITH SILVER TRIM. The footage has been remastered (a subsequent round of remastering in 2006-7). These versions, which began being sold in 2007-8, come with the completely new exterior space shots by the CBS special effects team of Michael Okuda, replacing all of the Jefferies original stock shots. Some of the new CGI shots mirror the old ones, but some are completely new (the ship from different angles, new closeups, etc.), but "in the spirit" of the old. All space shots were redone. The Enterprise is gray. The nacelles of the ship are shown with the bulb (but the bulb is "unlit"). The angles of the Enterprise orbiting is different. Many scenes on the planet (background, etc.) have been redone, some even reshot. The opening credits are completely new, using new CGI. In the opening, replacing the shot of the ship going to the right, then left of the planet is a shot of the ship going wide to the right of the planet. The music is redone, with a new vocal. Currently, only these remastered episodes are showing on syndicated TV, the old ones are off the air, nowhere to be found. These remastered ones are also the ones sold via Amazon direct HD.