So I bought Under Defeat yesterday after realising it's only 18€ (and 340MB, which is important on Switch). I've always liked this one but I kind of forgot how much as I had to pull myself away from it yesterday. It comes with three game modes, the original one from the Arcade/Dreamcast, an arranged one which I think they did for the PS360 HD release, and then the new mode they made for this version in which the game runs at full screen. I alternated between this and the original arcade mode and came to the conclusion that it's quite a bit harder in 16:9. I'm not exactly sure why but my guess is it's because you're closer to the action at all times as enemies pop into your view later than they would in other modes, while bosses have more room to avoid your shots and conversely force you to make bigger maneuvers to align your chopper.
I think I still prefer the original, but it's still cool to see something fresh in the package, especially as it makes the game shine in a new light. The last time I played it was a vertical slice of a 480p screen, so having a full 1080p rendition of it is quite impressive, and despite its age (20 years, sigh) it holds up phenomenally well. There's quite a few details I never noticed on Dreamcast, too, like your helicopter angling its shots downwards for grounded enemies, which wasn't really that apparent in SD.
Really happy with this release, runs like a dream on Switch as well, so presumably should do fine everywhere. I think I'm going to get it physically as well, I like what the publisher is doing here.