Both of them are fine! It depends on kind of service that you need!

Cheaper price? higher quality? internet Speed? local phone call? international one?Each of them has different prices , so it depends on u! 

I believe Telecom is better than Mobile

A lot will depend on what phone you have and where you bought it.

The 3 mobile operators use diffierent systems. (You didn't mention China Unicom in your post)

For 3G they use the following systems:

China Mobile TD-SCDMA ("Homegrown" 3G system,, actually bought from Siemens when they lost out of being the European standard)

China Telecom CDMA2000

China Unicom W-CDMA (Standard European 3G system)

4G is a bit more complicated as I can't find the naswer. Worldwide the standard is FDD-LTE while China Mobile has also developed TD-LTE.

It used to be that you had to be very specific when choosing provider. When I first came here I was given a China Mobile SIM card by the company which I used in my UK  bought iPhone 3G. I  could only get Edge data as the 3G systems were different.

The latest iPhone 5S and later ones actually work on all of them if bought in China. The 6, etc now work on both European and China 3G/4G networks.

So....post what phone you plan to use.....then you can check which one is best for you to use.

yes i had the same problem with my phone when i first came. I had a Note 3 that only provided Edge connection on a 3G plan using China Mobile. I switched to Unicom and it worked fine. 

For internet speed and bundles go for unicom. For cheap local use go for China mobile. Although imo China Mobile is crap.

China Unicom is not under consideration ? 

As touched on by Hotwater, phones bought in different countries will be compatible with different systems, which I believe is because built-in antennas are different to match the different wavelengths of the different systems. I had a friend who bought an iphone 6 in America and could only get 4G with China Telecom, not China Mobile, or something like that.