Ive talk about Hanyu Pinyin system several times before in my blog.  Attached below is a brief article that concisely explains in simple language how had Pinyin replaced Wade-Giles out of a relatively long journey of evolution. 

https://www.toutiao.com/a6488905494000828686/

I am not a linguist, not even close; but I think Hanyu Pinyin at least boasts of two functions combined: phonetic symbol(i.e. Zhuyin) and phonetic transcription(i.e. Wade-Giles).