I purchased almost half of the Oz titles available on Blu-Ray.
Let's clarify, there are five Oz titles on Blu-Ray: The Wiz, Tom and Jerry and the Wizard of Oz, Tin Man, The Witches of Oz, and of course, MGM's The Wizard of Oz. (The latter was released on various Blu-Ray editions, some including the extant Oz silent movies, the 1933 cartoon, and The Dreamer of Oz. These were standard definition prints, though, and were not released on their own. Hence, I maintain they're only technically on Blu-Ray.)
It took me awhile to get sold on Blu-Ray, and even though I do now own a Blu-Ray player, I can understand people still being satisfied with DVD. What sets Blu-Ray apart from DVD is the fact that it can contain a larger frame size for the video. Anyone familiar with printing can tell you that when it comes to images, bigger means better picture quality in the end product. Thus, a low-resolution scan will look poor when printed, unless you're doing it at a very small size. Market trends towards people buying large flat screen television sets eventually meant that DVD could only go so far before looking blurry. Hence, high definition video. Blu-Ray is now the medium for physical media containing such video. People who don't have large televisions are likely still happy with DVD, and that's fine. Size is relative, after all.
The titles I picked up were The Wiz and Tin Man. I'm not sold on high definition improving any aspect of Tom and Jerry or The Witches of Oz (though I might pick them up eventually), and the MGM film is getting re-released soon, likely with more bonus features, so I'll hold out for that. (And by that time, we'll have Oz the Great and Powerful and possibly Dorothy and the Witches of Oz available as well, I hope.)
Sam noted that each disc version of The Wiz gets fewer and fewer bonus features. The original DVD release had menu-based production notes and cast biographies that were dropped from the 30th anniversary release. However, that one had a CD of a selection of songs from the movie included. The Blu-Ray doesn't include that. However, a big plus over the DVD releases is that the menu isn't composed of still images, but a series of clips from the film set to "Ease On Down The Road." It says something when the menu has a better pacing than the movie.
While you're watching the movie, you can bring up the menu without interrupting the movie. (The options pop up, the background video and audio don't.) This is not available for bonus features, though. Trying to bring up the menu on those will take you back to the movie or the menu, depending on what you left behind.
And if you recall the exclusive bonus disc from Borders, all of its features are on the second disc, along with all the other DVD features from the standard version. While some online content (including a charming video of Kathleen Robertson reading the beginning of The Wonderful Wizard of Oz to children) never made it to home video, the Blu-Ray is likely going to be the ultimate version of Tin Man for home video, until they come up with ultra-high definition.
The menus are also accessible during the mini-series, but during the special features, it will offer an option to return to the main menu. (Accessing special features will stop the main feature's playback in this case.) Two huge pluses over the DVD is that this version contains subtitles, and there isn't a ton of trailers at the beginning of Disc 1.
Overall, if you make the jump to Blu-Ray and need to replace these titles (or you know, you want it because it's Oz), there's enough good about both of these Blu-Rays to justify a purchase. The better image, more special features on Tin Man, and the fact that with a bit of looking, you can find both for $10 each or less. (Both have been spotted in Wal-Mart bargain bins for less. That's not where I got my copies, though.)
Sorry that I can't provide compare and contrast screenshots. I don't have a Blu-Ray drive, and taking a photo of my TV would not make a convincing image.