In most speed-running videos, the person playing the game will usually play the Japanese version, with or without any knowledge of understanding Japanese. Is there a reason why they do this?
In particular, I am talking about traditionally Japanese games being speed ran, like Cave Story or Legend of Zelda.
Best Answer
There's a few reasons why a given release of a game (Japanese vs International, NTSC vs PAL) is used for any given run, and they change depending on the game. That said, there's a few common reasons:
NTSC (Japanese or US) instead of PAL (European): While this is less of an issue in newer games (AFAIK), the major difference here is refresh rate (which in itself affects frame rate). NTSC uses a refresh rate of approximately 60Hz (I want to say it's 59.94Hz, but for simpler math, let's go with 60Hz), while PAL uses 50Hz. Almost everything about a game in older games is tied around this refresh rate, so input checking, frame rate, and so on is all based on the "refresh rate clock". In the majority of cases, NTSC wins out for speed due to being about 17% faster, although there are a few cases where PAL is actually faster due to certain major time-saving techniques being unfeasible at the faster 60Hz rate.
Actual code differences/revisions: Certain games are actually more buggy in some releases (usually the older ones which are typically the Japanese release, although again, this has exceptions) and these bugs can be used for faster runs.
Characters-per-second in text: For games that have character-by-character text (e.g. Legend of Zelda), the Japanese version will usually see a significant time gain just by virtue of the use of kanji and the Japanese syllabaries (hiragana and katakana).