If you had a setup before that was running well...I would say that if it ain't broke, don't fix it.

I especially wouldn't change anything in favor of that Zoo-Med thermostat. I used one of those once upon a time, it failed, and had I not been home to see where the temp spiked to, I could have lost most of my collection. Others on here have had similar experiences. I personally don't feel they are worth the cost of the plastic that they are made of.

But to answer your question, I'd control the UTH with the thermostat and use the rheostat on the CHE. Doesn't matter what time of year, but you'll have to tweak the settings on both as your room temperature fluctuates.