This variation makes five points and leaves two ko threats. White can play at a first, and later at b.
Now White has only one ko threat, namely a. If we make the reasonable assumption that the area just above the corner is White territory, then the count living this way is the same. (White has a hanetsugi at a, Black has one at b.) Which is better depends on the circumstances, but usually variation 2 will be better.
Incidentally, should not be at b. See /Failure