pure has more power so you should almost always use pure except maybe in traps
I think the opposite. Pure should be used in traps (to do the specials better and faster) and dual in towers to do damage (more damage increase). But I am not very advanced in the game, so perhaps later I will see different effects than I can now.
Commented. Ill post a video of my try using 65 skill points on low level skills, killing the boss halfway through the first run. I really messed up my try, combining my gems to level 6, and then not having enough mana to reach level 7, followed by not even gaining 2k mana when the boss died for the other bonus.
