Looks like they're adding a few extras specifically for these releases, which appear to be ports of the PS2 SEGA Ages Collection anyway so yeah. Here's a quick rundown of the extra stuff.
-Sonic the Fighters will let you play as Honey the Cat (furry version of Candy from Fighting Vipers who was only in the Japanese version), Metal Sonic, Eggman (AKA Dr. "Robotonic" in this game), and maybe Super Sonic.
-VF2 has Dural selectable by default, it looks like. You can also switch the balance between 2.0 and 2.1, and I think it has the Arranged soundtrack from the Saturn version.
-Fighting Vipers has Mahler, Big Mahler, and Kumachan selectable by default. If we're lucky we might also get Pepsiman.
-Virtual-On has a bunch of new shit. You can play as the huge boss version of Jaguarandi instead of the Saturn one where he's tiny and fucking sucks, there's a Z-Gradt mode where you get to play as the last boss, a chibi mode, and a secret boss that can only be fought by clearing the game on the new Fierce difficulty without continuing and under 5 minutes. If you do this correctly, you'll hear Fei-Yen's Heart Beam noise after beating Raiden and fight the original Fei-Yen (the one in the game is a clone, this one is blue/purple to signify the difference) instead of Z-Gradt. The boss version plays the same except she's always in Hyper Mode by default.