they both have their advantages and disadvantages.
fire/cold/heuksal excels at pvp since it has mag def increase and phy def increse from cold and fire and it also hits pretty hard.
lightning/cold/heuksal wont suck at pvp but it wont be as good as fire cold heuksal. this build excels at pve because of mag attack increase from light and moving speed also helps a lot.
my build is heuksal 100/fire 100/cold 60/light 40 hybrid 5:1
I have a bit of everything and I do very well at pretty much everything, not the fastest leveler but still faster than a lot of builds, I do very good at pvp but still not the best. my build is very balanced in everything and thats why I like it. if u like to level fast then go with light, if u like to be good at pvp then go with fire, and if u like to be pretty good at everyhting, then pick my build
hope this helped
and in my opinion the damage difference between light and fire nuke can be compensated by lion shouts so it sld be fine 
