The herpstats have a extra safety feature that the ves do not the ability to turn on or off if you with an over shut down (common to all) but also an under shut down. If the probe gets pulled free for what ever reason the unit detects a sudden temp drop and shuts down the heat as well. The makes the need of a failsafe questionable.
I too would recommend a herpstat over all others my personal second choice is the ecozone thermostat I have only seen the herpkeeper a few times and the VE series only once but based on features I'd go herpstat especially as the cost of the two are so close it makes no difference.