Why do speed-runners usually use the Japanese version of a game?

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
Since you asked about Legend of Zelda specifically: Cosmo, the former (non-tool-assisted) speedrun world record holder for Ocarina of Time, released a very cool annotated video explaining the glitches and history of his speedrun.
At about 3m44s:
This run was done on the official Chinese release of the game. I chose this version because of faster text and less lag.
If you haven't seen this video before, I highly recommend it - it gives a great look into the world of speedrunning.
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Why are Japanese versions of games easier?
Typically this occurred due to there being a belief in Japan that Americans preferred harder games; often North American versions would have the lowest difficulty setting totally removed and/or an even harder bonus mode added.Why do Mario Odyssey Speedrunners play in Chinese?
Tyron also plays the game in Chinese text rather than English due to the Chinese text appearing faster and saving speedrunners a few seconds over the course of a run. Super Mario Odyssey is still quite an active game for speedrunners, with placements on the leaderboard as old as a week.Why is hollow Knight speedrun in Chinese?
This run was done on the official Chinese release of the game. I chose this version because of faster text and less lag.Are Japanese games 60hz?
As expected, Japan's classic PSOne games also run in the NTSC 60hz format, since Sony has opted to publish the original Japanese language versions of the games.Why Speedrunners Play on Japanese Releases – Version Differences
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Answer 2
Sometimes they use Japanese or American versions as they run in 60hz which way more faster than European/Australian (PAL versions) ones which run in 50hz.
It's 17% faster. This ratio is computed like this : 100-(50*100/60)
60hz means 60 frames per seconds, as 50hz means 50 frames per seconds. So with 60hz you have more frames to enter inputs (mostly used in tool assisted speedrun).
Take a look at frame rate on wikipedia.
Answer 3
All of the previos answers are correct, but Ill like to add something extra.
Back in the day when, when western companies didn't had any presence or subsidiaries in Asia, they would contract another company to do the Japanese or Chinese version. This would sometimes cause the Asian version to have more bugs than the western version.
A good example would be the Japanese PC version of Grand Theft Auto Vice City, which was done by Capcom instead of Rockstar Games. The Western PC release was on May 2003 while the Japanese edition was released a couple of months later, on September 2003.
The Japanese edition, due to being "less polished" than the original western release, has a lot of new bugs that are not present on the Western version and can be abused during speedruns to complete the game even faster. There is a thread on the speedrun.com forums explaining most of them.
Because of this, the Japanese edition is used on most of the categories of GTA Vice City due to being faster, specially on the Any% No SSU category (Script Stack Underflow is a bug that allows you to skip almost all of the game).
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