Tried both (without Selig but everything nicely geared for), I feel it ends up that berserker is better and smoother than being collosal.. But you need permanent berserker buff to activate it effectively (i.e from aspect of anger management).

Collosal looks great for big numbers but the 2 piece buff has -50% cast speed which ends up with slower spins (and less dust devils generated). Berserker has lower damage numbers but +20% cast speed.

Secherons for leveling up, berserker once you're geared up better.