I assume you’re talking about the XH-A1S?
The only difference is time-code in/out, gen lock and SDI output.
I have 3, and use the TC I/O regularly for multicam shoots.
SDI output is the main reason you’d pay the difference though. If you only want timecode to sync, you should save the cash and just buy a $20 slate and mark each take. Only buy the option for SDI.
I’d stay completely away from these cameras due to HDV, unless you were outputting via SDI to a truck, true HD deck or disk recorder.
The XF-100/105 look like fantastic upgrades…