Helix vs Herpstat

We plan on making an incubator out of a wine cooler and needed to know your opinions on these two companies. We have heard very positive things about both. Which is the more dependable one?

We were thinking about the heating element also. Some say light bulbs, heat emitters or flexwatt heat tape. The heat emitters sound the best. Put one on the top and one of the bottom of the cooler? Should we invest the money into the additional feature to make the temperature drop at night for bearded dragon eggs?

I personally like the helix models. I use light bulbs as the heat source.

Also, you don't want any temp drops on the eggs. The incubation temp needs to be a constant. Any drops or spikes in temperature can kill the eggs or seriously disrupt the formation of the dragons causing birth defects.

What temperature should the thermostat be set at? What are "safe" temperatures for the incubator to fluctuate between?