Most heating pads now a days will shut off every hour and they use more electricity and you will have to monitor the temp. The brew belt is designed specifically for this purpose and unless your temps come way up or down in your wine making area you will sustain a decent wine making temp.
I have used both and both work equally well. The heating pad has to not have an auto shut off. You will need to watch whatever it is you use and after awhile you will know when to shut it off.
You really can't just turn it on and walk away for 4 days.....
Always check on the temps as once your fermentation gets going you may not need any heat for days.
Then you will need it off and on for weeks until you finish degassing and fining.
Both work, but...
From a fire safety point of view, I would trust a brew belt before I would a heating pad.
One is made for warming wine, the other in definitely not.
Kelly, just becareful as this hobby becomes an addiction and then an obsession. I started in the fall of 2008 and had to expand the capacity of my wine cellar three times. I just installed a new rack yesterday because my seven hundred other slots were all filled up. I learned everything I know from just asking and listening to other winemakers on the forums. This is a great site and glad to have you here.