One advantage of learning the language can be catching some subtleties about the art. For example, the Japanese word that's been commonly translated as "block" actually has a deeper and more complex meaning than the English word, according to several sources I've read. It's got connotations of "receive" and "take" more than the "stop" of the word "block." It's also important to realize that Japanese can be a punners dream, especially written. Hatsumi of the Bujinkan, for example, has a reputation according to comments by several of his translators for really using layered meanings in his words. If you understand the language yourself, you may catch things that don't get translated with that depth...
Of course, I've only had to learn a very few words of any foreign language to learn my art... so I could easily be talking out of the wrong side of my mouth here!
Of course, I've only had to learn a very few words of any foreign language to learn my art... so I could easily be talking out of the wrong side of my mouth here!