I prefer snake_case() since it maintains a comfortable / familiar word spacing. Since I program mostly in Lisp, I use its equally attractive sibling, (kebab-case).

ToMeCamelCaseIsWayTooCrowded. ItMakesForUGLYEmphasis. AndTHISisJUSTmindBOGGLING.

Snake_Case_reminds_me_of_underlined_text, and is as-easy-to-read-as-Kebab-Case. Double_underscores__REALLY__stand_out and are reasonably_grammatical.

It doesn't matter as long as the whole project uses the same style.

Snake case, but it's entirely subjective.