Japanese, Korean, Chinese: Which Language is the Easiest to Learn? blog.gaijinpot.com

No, these are not the names of The Three Musketeers translated into Japanese but the labels for logograms—characters that symbolize a phrase or word—respectively in Japanese, Korean and Chinese.
However, since Korean is the easiest language to read due to its letter-based reading system, that also means Korean is the easiest language to write.
Following the previous point about speaking, you will find many diphthongs, homophones and subtle sounds in the Korean language.
With many vowels being close to each other in the Korean language, the pure syllabic sounds of the Japanese language means it wins this round.
I can definitely say that there are real benefits to learning Chinese, Japanese and Korean (at the same time, or separately!)