This.

As a general rule, flights are much stricter than trains.
Airport carry-on luggage scans [obviously] is the strictest check.
I once had my car USB charger confiscated at PEK, because they deemed it a weapon:



Train stations can be a pain, if there is something going on at the destination: i.e. if you travel to Beijing during one of their govt. meetings, expect extra scrutiny.
I've had to open all my luggage right on the floor at a secondary screening right before going down to the platform on a trip to Beijing.