I’m not familiar with all of them.
The Oz ViHadar has some excellent “Hagahos viTziyunim” on the side, which show both mareh mekomos and also textual corrections, additions, and re-insertions of text previously censored. These are not found in the slightly older standard Shas editions. It also takes other Rash”is found elsewhere in Shas and places them on the page for reference and to compare with the Rashis on the same words in the current tractate.
Also, the Oz ViHadar re-did the layout and text of the Ros”h, Maharsh”A, the Ra”N and others, and it is far more readable and clear, in my humble opinion, than the older format used in older standard gemaras.
In addition, the Oz ViHadar has some other nice touches both on and off the page, such as for each pasuk referenced on a given page in the gemara, the complete passuk is shown both on that page and, in the back, in the “Torah Or HaShalem”, is also shown there with some basic Rash”is, which gives the learner some context and basic explanation of the passuk.
Finally, like some other editions, the Oz ViHadar combined many of the smaller commentaries into one “Yalkut Mefarshim” browsable in the gemara’s page order, instead of giving a page or two to each and making the user search through each one individually as done in the older editions, which is far more time consuming than Oz ViHadar’s and some others’ way. There may also be some other acharonim in the yalkut that are not in some others.
Artscroll is best known for its English translation and associated commentary on facing pages, both in-line with the English transaltion of the text and expository comments below it. It is otherwise essentially the standard Gemara, minus all the commentaries in the back, but does have, on the page, Likutei Rash”i which bring down Rash”is on the same words that are found in other tractates, and Laazei Rashi which translates the Old French words occasionally brought down in Rash”i.
I’d personally recommend both, for many people. The Oz ViHadar is a beautifully done gemara with many mefarshim and enhancements, and the Artscroll can supplement that with an excellent translation and commentary, both running commentary in-line with the text and expository comments below the text.