Hi,
Linear Throttle Response should be more safe, but Fixed Wing can utilize also autorotation bailout.
If you do not plan to use autorotation bailout, then linear throttle response should be good.
Pilots with V4 are reporting some problems with external governors, but there are pilots with Spirit units that are successfull.
You can check this thread:
http://www.spirit-system.com/phpBB3/vie ... 5&start=70
First from all I recommend to update ESC to the latest version.