I prefer a water bath and an aquarium heater. The water conducts heat much better than air the temperature is much more controlled.
I have a detailed blog post coming up on this.
Here is the heater I use:
Fluval M 50-Watt Submersible Heater
It works great. The temperature in the middle of the ale pail was within 1 degree of the water temperature just outside the pail for the entire fermentation. I brewed a Sasion with this at 70 degrees in my 60 degree basement.