Which prepaid sim to get?

Hi, I am staying in HK for a few months. I mainly use it to surf the web on the MTR. I spend about 4-5 hours/week on the subway. I usually do not make phone calls. I will do some whatsapp, LINE, FB communications. Which prepaid sim card do you recommend?

Recently I got a CMHK 4G/3G Super Talk Prepaid SIM Card.

http://www.hk.chinamobile.com/en/corporate_information/Prepaid_SIM/local_users/prepaid-services-4g3g-localtalk.html

I have not activated data plan yet. If there is a card with a better deal, I will get a new one. Anybody knows the differences between my current card and the 4G/3G Data & Voice Prepaid SIM?

http://www.hk.chinamobile.com/en/corporate_information/Prepaid_SIM/local_users/prepaid-services-4g3g.html