This sounds like a great reason for an experiment! I'm not sure that it is the brand of popcorn, but possibly the type of corn used, and how it is prepared in the container. You could find out by heating all of these popcorns for the same amount of time, counting the number of popped corns, the number of corns that did not pop, and seeing what percentage popped. I'd love to know the answer to this one!

Popcorn kernels contain water, as do all living things. When you heat them, the water boils and turns to vapor (gas), but the gas has no where to go because it's inside of the kernel. As a result, it expands violently, forcing the kernel to increase in size until the water either escapes or the kernel is big enough to hold the water vapor, which is the popping.

I'd suggest that you design your own experiment to test which brand of popcorn gives the highest proportion of popped kernels. The key to popcorn is actually water. Inside each kernel is a small amount of moisture that, when heated, turns into steam. As it turns into steam it expands, causing pressure to build up inside the kernel. When the pressure inside the kernel is great enough, the hard outer casing of the kernel breaks. Then the kernel "pops", turning inside out to form that yummy snack that we all enjoy while watching movies.