Are "hotter spark plugs" a rip off?

I'm pretty sure that as long as you HAVE spark, ANY spark, that is all you need in the combustion chamber. Think about it, if you're in a house filled with natural gas, any size spark will ignite the whole place. A bigger more powerful spark won't make any difference. One time I was at Auto Zone and one of the employees tried to sell me this whole "ignition package" that was supposed to up my gas mileage. He said he had it on his '79 Bronco with a 390 V8, and he got 22 miles per gallon. I call BS. Is there any evidence to back up this "hotter spark" debate?