I stand firmly by the position that using both light and dark has no inherent advantage over pure dark or pure light.
Using both light and dark is not inherently stronger or weaker than purely use one side or the other.
People assume a Vaapad user is tapping 100% light and 100% dark, it doesn't work that way.
Each individual still has a limit to how much they can channel the force, so maybe they are doing 50/50 or 60/40 light, versus some one 100% dark. The percentage of light to dark they channel doesnt dictate their power so much as their expertise is utilizing the force and the amount they channel.
Juyo is an incomplete form for jedis because they cannot fully use it, in fact they can barely use it with all the restraint they have in their teachings.
Vaapad is made so jedis have a variant of juyo to use, to draw on the very edges of darkness and convert it to light side which than powers them.
I'll make this clear, Vaapad users DO NOT channel the dark side as their power, they tap the edges of darkness so they may draw on it and convert it to light side energy which than fuels their power.
Juyo users 100% channel darkside energy and use it 100% to power themselves.