Each poem is written in a certain way which is best for the opinion that the poem is trying to get across. The charge of the light brigade talks about each part of the battle, this means the author can the show how the men were courageous in battle. Dulce et decorem est however only talks about the after effects of the battle. How men had died and were dying, how they were fatigued and bloody. This is a point of the battle, which the first does not talk about to a great extent.
The poems also differ in the way that they are structured. The charge of the light brigade tends to be in a more uniform fashion with all the paragraphs laid out evenly with the same number of lines in each. It also tends to keep a certain pattern in the rhyming. Dulce et decorem est however is less organised and tends to be set out as according to the poem, for example the two solitary lines were it talks about the soldier who has been a victim of the gas attack.
Overall I think these two poems get across the point that they are trying to portray very effectively in their own ways.