Mostly depends on my mood. I play a lot of old games in emulation and my monitor is 32″. If you’re going to play Metroid 4 or any other GBA game on it, you want an LCD effect.
I’ve had very mixed results using the “shaders” which is Retroarch’s word for “filters”. I like the LCD one, and I found a generic “CRT Hylian Glow” one that I like for nearly everything that isn’t the GBA. Unfortunately, there are a few emulators that seem to crash with that filter applied (Dreamcast) and my hand-me-down PC I use for emulation doesn’t have enough CPU/GPU overhead to apply a shader to GameCube and not drop frames, so those are raw.
I also liked using the CRT shaders in Street Fighter 3: Third Strike Online Edition. And the composite filter in the Mega Man Legacy Collection is great!
But I didn’t like the filters/shaders in Sonic Mania and just cut my eyballs on the raw pixels and you know what? My eyeballs liked it!
If the scaling isn’t integer, things get ugly fast!