This applies to a fixed flow rate system like the AEM or boost powered system, and running a larger flow rate for WAI then WI as suggested.

(1) WA is better in summer than WI because of the cooling of the meth evaporating.
Less different in winter.
(2) Power and smoothness above peak torque is better with WAI.
(3) When only tuned for WAI at your highest boost and still running it at lower boost,
it will cause misfires from being too rich. (My Blitz allows 4 boost levels.)
This is the only event that WI is better at as I have not had any low boost misfiring from being richer.
(4) No possible leaning out of WI if car sits for a long time in hot conditions as no meth to evaporate from the mixture.
(5) WI liquid will not burn but you can light off 50/50 WAI mixture.