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.
The missing 54 stages from the two 'NEW STAGE' DLC have been added for a grand total of 305 stages, of which 84 are DLC.
Bonus fact: The Battle of Liang Province has both an original and DLC version. Amazing!