If just looking at the Xeno attack Shisaguard is better, as its only costs 160 TU.
However, you can try it, when the opponent has a Wind Ark in the line up, Shisaguard’s damage output becomes EXTREMELY poor. Chopperbug’s timestrike may do better than it. And there are many Wind Arks, chopperbug, grem knight, raioh, don, typhoonwyrm, stegospike etc.
Its Mystic Bane is useless.
And being a beast, Shisaguard’s survivability is actually not that much higher than Snowja.
Snowja’s moveset is much better. And he looks cool!