I compared the two in certain locations where you have to wait for dialogue. English was faster in all four.

Uprising at Chang'an Intro: Diaochan, Dong Zhuo, Lu Bu, Private, Diaochan, Wang Yun English ~44 seconds Japanese ~50 seconds

Uprising at Chang'an Bridge: Zhang Liao (x2), Lu Bu, Messenger, Dong Zhuo, Wang Yun (x2), Dong Zhuo English ~56 seconds Japanese ~63 seconds

Capture of Puyang Intro: Lu Bu, Chen Gong, Lu Bu, Chen Gong, Zhang Miao English ~42 seconds Japanese ~50 seconds

Battle of Dingtao Escape: Xiahou Yuan, Chen Gong (x2), Lu Bu, Chen Gong, Xun Yu English ~48 seconds Japanese ~59 seconds

And then I grew tired of comparing and I'll just assume English will be faster in most, if not all, the other cases.