This is a port to PS4 of the PS2 version (see entry 1348) of KOF '98 Ultimate Match. It runs in 1080p, and overlaps the previous animation frame with the current animation frame (this is sometimes called "interpolation" or "blending") to make the character shadows a solid 50% effect, rather than the old-style black blinking effect they have in the PS2 version--but the side effect of this is you do see a partially transparent version of the previous frame of a character's animation, a sort of "ghosting" effect.
I used to hate that, but with my eyes being sometimes a bit photosensitive these days, the smooth shadows in this version--particularly because shadows here are rendered behind the characters, rather than below them as in, say, KOF 2000--are very helpful, especially because in the game's NEOGEO Mode you can also turn off Supers and the Super Gauge UI, which would normally distract from the shadows a bit, if not actually cover them as they do in 2000. It's pretty keen to be able to run the game in NEOGEO Mode with the Super Gauge UI out of the way, and smooth shadows. : )
Another difference (I think--unless I just did it and forgot about it when I first bought and downloaded the game months ago : o) from the PS2 version is that the unlockable characters like Kasumi, Eiji, and Shingo are available from the get-go here, in UM mode (of the UM modes, I only play Practice Mode, since that's the only one that lets you turn off Supers.
For some reason, I'd never noticed that NEOGEO '98 lets you turn off Supers! Man, that makes my eyeballs happy. Now I can play '98 again! 8 D
One thing about 98UM: the difficulty, at least in the enhanced "Practice Mode," is a little low: UM's difficulty only goes up to 7 (whereas the original '98, accessible here via the "NEOGEO Mode," which gives you the original AES home version of '98, goes up to 8--and if you really need a challenge, the Survivor mode in NEOGEO '98 is even way harder than THAT--and if you need still harder, holding eh Start or Select or whatever touchpad mapping it is in the PS4 version while picking Survivor gives you an EVEN HARDER version of Survivor, for pretty much the toughest challenge of any KOF ever), and at 7 I can get pretty lengthy win streaks in "speed battles" in UM's Practice Mode.
Huh okay I'm not sure you can access "harder" Survivor mode in NEOGEO mode of KOF 98 in UM, 'cause they've hard-mapped select to the PlayStation's X button--whereas in the actual NEOGEO version, FAQs tell me that you select "harder" Survival mode by pressing A (light punch) + C (hard punch). I've tried various things like mapping X to Light Punch and pressing it along with my Hard Punch button, or even mapping X to Light Punch + Hard Punch (the Controls menu even in NEOGEO mode is not the actual original NEOGEO controls menu, but a fancier UM one), but I still seem to get a Survivor mode of about the same difficulty as ever.
I guess I don't actually want to play Survivor mode anyway though, because unlike tbe other gameplay modes under NEOGEO mode, Survivor ignores your Power Gauge ON/OFF setting--it always has Power Gauges enabled. : P
Ah, now I'm starting to recall some of the flashier, less eye-friendly aspects of the game. In UM's training mode, set up as one-round battles, lettering--"GO" or something--flashes in the middle of the screen before each round; it isn't actually that bad, but what's worse is that the combo counter flashes onscreen, blinking every time someone does a combo, which is pretty often. And in NEOGEO mode, pretty much every UI element flashes as it appears.
Aha, and I finally hit the bug present in the PS2 version, which I was hoping was magically fixed here, but isn't: although you can set character selection to "Boss Cut" in UM's Battle Config, which prevents a random selection--which you can make on the character select screen by holding oh it's L1 or R1, I forget--from picking an actual overpowered boss character--namely Omega Rugal, among the characters available by default here--the "Beat" random selection the Practice Mode does to replace defeated characters, or just its own between-round random selection setting, *ignores* "Boss Cut," so even with "Boss Cut" set in the game's Options, Omega Rugal may still materialize between rounds in Practice Mode, ruining your little "speed battle" set up until you go back to the character select screen and re-pick characters yourself. : P
I think I was wrong about not being able to access "harder" Survivor: if you hold Start while selecting Survivor, you can't continue once you're KO'ed; I guess that's the harder version.
Forgot to note that this PS4 port, unlike the PS2 version, does frame interpolation to blend the NeoGeo's normally flickering shadows into a smooth 50% transparent effect--but it also introduces a "ghosting" effect as the characters move, particularly visible as they whirl their arms and legs around quickly.