In my experience? For writing, .pdf is always preferable.

I prefer txt , dont like to dowload story on my phone before reading it

you can use RTF is supported by most e-readers and i think FA also has support for it.

oh nevermind. looked at a old upload i did and it doesnt support it either.

PDF can be opened natively in most desktop browsers as well (Chrome, modern Firefox, Edge, Safari, Opera), and txt can be downloaded for later. Just wish mobile browsers would get with it on native PDF rendering, since they usually don't allow Javascript to run.

As for file format, use what you feel most comfortable with. I use PDF since it allows for proper text decoration (it's all typesetting), but if you really don't need the features it holds, why change?

I should probably use PDF tbh.

Up to you. I never usually read stories on FA unless it's on the computer, and I always upload in txt myself. Pretty much the few times I uploaded a story in a document that WASN'T txt (either a doc or an upload of a friend's PDF story), I tend to get a complaint or two XP

I usually like to read before faving so txt seems to work best

PDF is one of the few I don't mind that aren't auto-shown. I do like the ones that auto-show, though.

Honestly, TXT is the way to go. I'm not a fan of having to download before reading. A better solution is to include the PDF version as a download link in the artist's comment rather than being the thing itself.

I'm strongly biased towards .txt , but it looks like you'll have plenty of supporters for your decision either way...