Hidden simply trims clutter(or for others, information) out from the screen, compared to HR and DT which alters the beatmap's values like OD, HP, AR, or duration.
I thought that what ever I can do with Nomod, I can do with HD too, but it turns out it hurts me during aim-heavy streams and cross-screen jumps. It's not that bad though, I never got stuck because of HD since it's similarly linear in difficulty progression with Nomod, compared to DT which spikes around high ARs. Instead, I got stuck with DT before lol (kids that's why you don't play DT only).
On the other hand, HD trained me to listen to the music rather than relying on approach circles, and helped my muscle memory a lot since objects don't stay on the screen for long.
my scores already says a lot about me