First build is more fun and gimmicky than it is useful, but its fun to play and makes me feel like a Mesmer from GW.
Works pretty obviously you go in and use illusions to survive. Not very successful against elites, but fun none the less and is actually really good on bosses.
Second build is more serious and takes advantage of Arcane Dynamo.
Living Lightning hit a billion or more times each cast so it procs Arcane Dynamo a lot allowing you to arcane orb for insane amounts (at least in Hell mode). Also I'm not sure how Venom Hydra works with Arcane Dynamo because I know it uses the procs, I'm just not sure if it increases each of its attack for the whole duration or just its first attack.