SMD stands for Surface Mount Device. It's a way to package ICs that are being used in the SPL meter so that they consume less space on the PC board. Also, there are machines that are used to mount these ICs & solder them (i.e. it is automated) hence the lower cost. SMDs were done mostly from a manufacturing cost stand-point.
Functionally, the SMD parts are identical (& many times better) in functionality.
Per Rives' response, perf. from either SPL meter is identical within the limits of their measurable tolerances. So, in practise, both SPL meters are identical!
My conclusion: buy the latest analog SPL meter & use the same SPL correction factor disk from Rives to account for the low & high roll-offs.
Hope that this helps.
