I was reading up on Rockstar's support pages, and found this: https://support.rockstargames.com/hc/en-us/articles/200195177-How-to-change-the-language-in-Grand-Theft-Auto-V

I became instantly interested in figuring out weather or not any of the other languages were faster. I experimented with getting to franklin and lamar's split, and it was almost 6 seconds faster than the english version. I need to do a bit of more experimentation, but I'm quite shocked at how much speed I got from just changing the language. You have to change it in your console's settings first, unfortunately.