Some of this is actual info, while some of it is assumption.
For one, it would allow for a faster casting rate, a variety of equipped spells in a situation calling for more then one type of spell. Similar or exact same spell can be put on both hands and combined to make a more powerful version of the spells.
I assume you also know about the flamethrower effect of the fire spell when held down and the aditional effects of elemental spells, such as lightning draining MP and frost slowing down opponents and draining fatigue.
May God have mercy on your soul... - The Preacher Because I sure as hell won't. - The Gunslinger
I seem to recall them saying it already was in the game... >__>
You recall wrong.
"The ability to equip two different spells on your left and right hand raises the question can you combine more than one spell? We're not talking about that, Howard says with a smile. We're not sure. We'd like to; it'd be awesome."