Actually, SoV is the one that is constant holy damage as the dot always ticks (never misses on the DoT portion) while SoR is subject to miss/dodge/parry depending on your hit and expertise levels.
Both are affected by that talent for 15% more damage.
The answer is they are both pretty close, though SoV will win out eventually as it scales better with AP, which we have more of than SP typically. Plus, 10 expertise skill from the SoV glyph is very nice in the long run. That is a lot of itemization points.