One suspects the ring effect is a representation of a 720 degree bubble of energy expanding out from Praxis. Instead of expanding sphere, we get to see just a slice of it as a ring. (Rings of destruction look cool and don't block out the rest of the explosions and stars like a bubble would)
I thought the expanding sphere effect in "Generations" looked pretty good.
And wasn't there something similar in ST09?
But the energy ring in TUC did look pretty cool and menacing.
Kor