Simple question ( I think)

Simple question simple answer no there is not

With most systems you can run the memory in dual channel mode with 2 modules, which is faster than single channel mode. With the larger single module you leave more memory slots open for potential future memory expansion. If you don't ever expect to go beyond filling all of the slots with 4GB modules, then going with 2 X 4GB makes sense.

Most recent mother boards and their chip sets require 2 or 3 ram modules for best performance. These are usually represented by ram slots of the same color. That said it is rule of thumb to use the least number of ram modules as possible. So if the MB offers 4 slots and you want 16g of ram it is "better" to use 2x8 rather than 4x4. Voltage and timing regulation is tighter for fewer modules. This is especially important when over clocking of the ram is planned.