One thing to consider with the F1 is the remix decks and STEMS control that’s already built into it. You can switch the profile(from native to custom in the prefs) of the controller if memory serves and bounce between using it for FX and it’s native format.
As to the twister, I cant say I love the idea of controlling FX with dual encoders/buttons, but that might not bother some, and having an encoder per button to tweak FX values is nice. You could also do some pretty cool stuff by applying the built in sequencer to an effect in Traktor.
The F1 used for FX is more a traditional grid controller. I prefer to map a series of FX values over a row in the grid, so it works better for me than I think a Twister would. Also having a MIDI mappable 7 segment display is pretty nice.
F1’s are also cheaper and easier to find used than a Midi Fighter, and they have those nifty metal stand/case things that bring them up to mixer/CDJ height.
That said, If you don’t have a step sequencer on hand its a great thing to have. I picked up a Beatstep Pro when they came out, so no need for that in my rig, but if you don’t have something similar, The Twister may be worth it for that alone.
I’ve got a MF3D and an F1 and both are quality. If I could have only one I’d probably go for the F1 as for prepping and using remix decks there is nothing quite as good. That said, the MF3D is currently in my live rig and the F1 stays home and gets used for prep tasks only - the MF is just nicer to use and takes up less space in the bag.