The snapshot file shows data from several different points in time. The time may vary. Normally, snapshot_sysinfo files show a bunch of daily snapshots, and snapshot_sysinfo_stats files show hourly snapshots. But customers can change the time intervals.
System_information files show several things that one will not see in the various snapshot_sysinfo files. The system_information has Hardware information, software configuration, the policy setup and some eventlog data (shortened from what the eventlog has in it)