One of the main novelties of Awakening is the option to turn off the permanent death early in the game. This mode is supposed to players who have never played any of the games in the series, but can be advantageous for all players, especially those who do not want to ever worry about keeping all living units, those who never liked this system in previous games or those who know that this system brings some flaws in the continuity of history and also do not want to think about it.
Although the characters can die in reality we must do everything in our power to prevent this from happening as it is obvious, therefore turns out to be the difference between choosing a mode where it does not happen at all or to constantly reset the console and recharge a game before.
Unlike many games in which we have a number of units equal to all who serve sometimes as "cannon fodder", basically all RTS market in Fire Emblem all units at our disposal are an integral part of the story and is supposed win some affinity with these characters and do not let them die. Therefore it is to play the Classic mode is much better because it does not really want to walk the constant resetting the console and repeat a few minutes of the game, but the danger of losing a character makes each scenario is a battle more intense that playing in the new mode.