Are there any comparison charts for GDX, nBlood and BFS? Something akin to
these.
Why to prefer nBlood over GDX, for instance? Especially if I don't have any allergy to Java's libgdx.
GDX has the best menus, user interface and customizability. You can run custom content and Cryptic Passage in-game without having to shut down the game first, and all custom missions will work on GDX without any problem. Rebinding controls is very intuitive compared to vanilla as the two possible inputs for each action have their separate menu column, so you don't have to rebind an action twice to undo a second binding if you just want one. You can enable the option to see the level name and its author at the start of the level, so you know who to bitch at. It boasts the ability to perfectly replay Blood demos recorded via the vanilla version, so it's probably the most accurate port of Blood to date. Also has stuff like autosaves and save previews.
However, it lacks stuff like a FoV slider, the ability to realign your crosshair with the actual center of the screen, and seems to lack raw mouse input, as mouse aim in GDX feels really off which is a major dealbreaker to me. It also has a custom difficulty settings, but it's fucking borked. For example, if you set the enemy quantity to Extra Crispy levels, you will still get Lightly Broiled amounts of enemies unless you set both Enemy Damage and Enemy Health to Well Done or Extra Crispy, which kind of defeats the point of a custom difficulty. It also gives you the option to automatically pitchfork start each level if you plan to do a pitchfork start run, but even with it enabled your health will still carry over between levels, which to my idea seems to ruin the whole point of doing a pitchfork start run.
nBlood is kinda new so it's not 100% accurate, but probably will be soon. It does support FoV sliders and mouse aim is perfect here IMO, though it lacks all the QoL options and menu options of GDX, as you still have to load Cryptic Passage and other mods from the launcher. Currently my favourite, if only because of the good mouse aim. I also can get playing the MIDI music working with it just fine, whereas in GDX I can only get the redbook music working. I don't know whether this is something I fucked up on my end though. nBlood currently doesn't support movie playback, though you're not missing out on much anyways.
Fresh Supply/KEX/EX/whatever boasts the best multiplayer component currently available, though even on its own it's kind of spotty with frequent disconnects and being lacking in options. Unlike GDX it also has a custom difficulty settings that actually works, and even allows you to tweak more individual factors such as enemy aggression and accuracy, which makes it my go to if I want to play the game on Well Done with Extra Crispy enemy quantities. You get a FoV slider and the ability to enable ambient occlusion, which might make the game look better depending on your view. The HUD can be realigned to a 4:3 aspect ratio, which is useful primarily if you're playing with an ultra-widescreen setup. Many level details and objects have received new 3D voxel models which look great in my opinion. You also get HUD indicators for how long power-ups last, which is especially useful for the invincibility power-up as it had no visual indicator for when it would run out. One of the nicest things about KEX is that getting crushed between doors will no longer instantly kill you, you'll just get pushed out. It may not be accurate to the original, but hey, I'll take it.
That said at this point of writing accuracy-wise the port is still sloppy. They're hard busy on fixing it if the speed and size of the last update is any indication. But for now you might suffer from crashes and glitches which were never in the original. The weapon switching delay is now longer too, so you can't quickly switch between another weapon and your shotgun to quickly reload a single shell. There are some reported compatibility issues with custom missions like Death Wish, so full compatibility isn't 100% guaranteed yet. It also misses the option for HUD elements like a secret, kill, and time counter for some reason. There are a lot of miscellaneous bugs, like crushers going up being able to kill you, Phantasms not emitting blood on being hit, masked textures blocking your bullets, and so on. It also gives me shit when I try to Alt+Tab.
If the mouseaim in GDX doesn't bother you, then stick with it, otherwise go for NBlood. If you want to play multiplayer or really want a custom difficulty setting, go with KEX.
EDIT: GDX has just been updated with a FOV slider and fixed custom difficulty, so go play that one.