By entering this as an array formula, you are "looping"
through the ranges, returning either a 1 or a 0 (if it's
1*0 [true for criterion 1/false for criterion 2] or 0*1
[false/true] or 0*0 [false/false], the answer is 0; only
if it's 1*1 [true/true] do you return a 1). The SUM
function adds up this array and returns a single number
indicating the number of times both criteria hold true.
There's nothing particularly "better" about this method
than yours. It's less text, and in essence only 1
equation (as opposed to 2 COUNTIFs). It's also (imo) a
bit more intuitive upon sight. Personal preference. It's
the only way I could think to "clean up" your equation.
Not sure what else you might be looking for...
Good luck,
Karen