There are four brandish lines and all of them offer great power and speed but when it comes to choosing one I would go with shock. Now I have only used shock and shadow but I have seen all of them in action and I believe shock is the best but that's just my opinion. Please comment which is your favorite brandish line and why. I will try my best to reply to all of you as soon as you post.
Why I chose shock. Out of the four(five if you include obsidian edge as an extra line)brandish paths I would always chose shock but I believe the others are good too. here's my list of brandish rankings(forgive me if I get the names wrong). 1. Voltedge 2. Glacius 3. Obsidian edge or Achreon 4. Combuster. The reason I put fire last is because it is just doing extra damage, for example freeze keeps them in one place, shock does damage and interrupts them, shadow does lots of damage and poisons them but the combuster just does extra damage. Don't get me wrong I'm not saying its bad I'm just saying its not the best from my point of view. Both obsidian weapons do lots of damage and the obsidian edge poisons them. Glacius keeps them from moving around. but shock does almost as mush damage as fire and can stop them in the middle of their attack. That's why I chose shock.
There are six Brandish lines. They're not directly comparable to each other, because of the difference in damage type. If you want to focus on the three elemental lines, then my answer is here:
http://wiki.spiralknights.com/User:Jdavis/Swords#Elemental_Swords
Spoiler alert: Still Combuster, although Voltedge is good too.