Personally I think the bandwagon on this front is a bit overwhelmed. Been using a 15+2x10 for 15 years. And the 2x10 goes on the bottom.
The cabs are matched, so they were designed to go together.
I think the bigger issue is when you mix brands/series which is perfectly understandable that the different characteristics of mixed brands would cause problems.
Studies suggest that vertically stacked drivers of the same type are less problematic of phase issues and will give a better sound as every driver is designed the same and working together.
IME, a 115 pairs up MUCH better with a 210 than it does with a 410...
