According to my teaching experience, I would prefer Yale. There are four romanization systems, they are Pingyam, Yale, Jyutping and Sidney Lau. In my opinions, the tranditional Pingyam is the "worst", however, there are books still using this old school romanization system.
For example the word "girl" - neoy4 (Pingyam) , neui5 (Yale) , neoi5 (Jyutping), nui5 (Sidney Lau)
Although there are slightly different between Yale, Jyutping, it make much sense to locals when you type neui5, instead of neoi5.
Also, take "like" as an example, if you type Zung1 ji3, most of the HK people will be confused; but if you type Jung1 Yi3, most of us will understand what you mean immediately. Considering most of the foreign prefer not to learn the characters, so it makes a big differences when you want to make some sentences by using romanization system.
For you reference, you can see the difference between 4 randomization system by visiting this website.
http://cpime.hk/pingjam/