They are both excellent. the herpstat nd was more feature than the helix, with the max watts at 600, night drop built into the unit, 1/10 degree temp setting, high and low temp level alarms, power outage detection plus many other features. makes this one a great thermomstat for incubators and works well for racks or single enclosures. the helix is simple to use, 1 degree temp setting, this one been used by pro breeders with a long excellent track record. I have both, I had a big power surge from a storm which blew out T.V.s, alarm clock radio, computers, my oil filled heater for my snake room. But all my herpstats and helixs were on when the surge hit, which was months ago and both types are still working fine.