Katz, neither one is necessarily a bad feed, and Checkerboard Square (Purina) has the sales numbers on both formulas to prove it. Are there better, more consistent products on the market? Yes, but finding those other brands in certain areas is a real challenge.
Because Purina is instantly recognizable to most people as it relates to animal feeds, they're going to sell product, but showmen wouldn't use it like they do if it wasn't a good product. I cannot imagine that doing a 50-50 mix of the two and feeding it would be a bad idea, but I'd refrain from just pouring one on top of the other. IOW, mix them together thoroughly in equal measured amounts in a bucket before pouring them into your storage container. Just pouring one on top of the other could amount to constantly doing a change of feed, and that's normally not good.