It's not what you fight with that matters, it is where you will fight.When someone strikes at you, you've got many options: Dodge the blow, Parry with a weapon or block with a shield. From these three options, you can always yield back by one step and get +3 to Dodge, or +1 to parry/block. Remember that a medium shield gives a +2 to any types of defense, not just block. This means that for as long as you can give away terrain, a fighter with a shield has a +5 bonus to dodging. For a "normal" person with some encumbrance and a Dodge of 7, this means a final Dodge of 12, or 75% chance to avoid being hurt. This also applies to your opponents, so there is value in trying to corner your foes as soon as possible (where they will Get Dodge-9, or 37% chance of success).
Against missilesAgainst arrows and bolts, you can always "hit the dirt" and dodge with a +3 bonus (plus shield bonus). The downside will be that you will find yourself prone on (-4 to attack, -3 to defend, but from now on at -2 as you are a smaller target). Getting back up will cost you two turns, and this can be a long time in some situations.
Getting Fancy: parrying and blockingParrying and blocking can each be used only once per turn (1 second). They usually will be more potent than dodging since they are not affected by encumbrance. The down side is that both your weapon and your shield may get trashed in the process. Weapons made of steel shouldn't break unless parrying a critical hit kindof blow, or a very large and spikey weapon. A typical shield could get dinged when blocking strong blows, and require that you fix them up every now and then. It is unlikely that a shield will fall apart without any kind of warning, unless you block a battling ram with both hands. Also, unbalanced two handed weapons can only parry OR attack in a given turn.
Of course, working as a team to use up the better block with one allies and forcing a dodging of the second attack is even better. But fighting as a team is a whole story in itself.