I personally prefer to play fire TB for dealing damage, Ice is nice for disables tho.

I prefer hybrid. Fireball -> Fire Nova -> RoI = ouchie.

I tend to see more Fire TBs for the burst damage and fire aura, but frost TB is equally useful IMO.

Ice TB mostly, Fire TB sometimes, I really wanna learn Fire/Ice but I haven't gotten around to it.

Fire is great and definitely pumps the most damage, but the ability to totally control the landscape as Ice is hard not to be enticed by; you can maul pretty much every DG or build that relies on skills with a cast bar, you have an almost 100% out all of the time, and the damage of stacked debuffs and 3X Shatter's is a lot higher than most people think.

I almost always play the TB as a hybrid.  Seems a waste to give up either fireball or rain of ice, as both are absolutely fantastic skills that are hard to live without.  That and you need to constantly change forms anyways to keep his mana regeneration up.

You're not always attacking, so you don't always need that one, but you can always use extra mana regeneration.

If we could move while changing forms, like QoT, I'd definately go with fireball for my ice build.  Otherwise, I can't use it to fire at retreating enemy demigods because of the time it takes to switch forms.

I've tried that and can't figure it out.  If I move while switching forms I get an interupt, leaving me in the original form.

I also play hybrid TB. RoI, Fire and Ice, Firenova. frost aura 3. Sometimes frost nova 1 instead of fire nova 3 if it is a tower rook. Great at farming and beating everyone to 17-20 which is when this build shines. Most tbs I play with or against dont switch forms ever the whole game...I am constantly switching even in combat. With frost aura on I move a bit hit fire do some combo action and go back to ice and reaply frost aura and another combo. RAWR

I scream, you scream, we all scream for ICE cream

Fire has the potential for a lot of damage in a short amount of time. Ice has a ranged AoE with nice damage, a stun and a disable (if you use shatter for damage you are doing it wrong). The various hybrid builds have the best of both worlds though aren't masters of either.

What it boils down to is taste. Personally I'm always playing Ice TB (and always TB on top of it), I found it to be most effective for my own approach of playing this game.

Simply try out what fits you best. Try pure fire, try pure ice and try several hybrid builds. Stick with the one you perform best with.