  In this paper, we compare the Akashi series of the Pontryagin dual of the
Selmer groups of two Galois representations over a strongly admissible p-adic
Lie extension. Namely, we show that whenever the two Galois representations in
question are congruent to each other, the Akashi series of one is a unit if and
only if the Akashi series of the other is also a unit. We will also obtain
similar results for the Euler characteristics of the Selmer groups and the
characteristic elements attached to the Selmer groups.
