When duel wielding, the use of both weapons at once is very effective against the smaller enemies, but for attacking the more dangerous enemies or large numbers it is best to fire one weapon until it is empty and then start with the second. For certain weapons like the Brute Plasma Rifle and SMG the reload time is very close to the time required to empty a clip or overheat. By doing this you can maintain a constant stream of fire and supress many enemies at once.