Hangzhou to Suzhou OR Hangzhou-Shanghai-Suzhou

Hi
We are family of four(2 children). We will be in Hangzhou (from Xian) and then Shanghai. We wanted to visit SZ too but wonder should we break the trip Hangzhou-SZ-Shanghai or Hangzhou-Shanghai then day trip from Shanghai ? As from what I read, looks like train connection are better from Shanghai to SZ instead of Hangzhou to SZ.
Thanks