The Round Shield protects your sides a little better against archers, not all fire is going to come directly in front of you.
That said, I use the Horseman's Kite shield and it is very solid, it holds it's own against the more expensive/higher difficulty shields in Battle, at least.
weight: 5
body armor: 16
difficulty: 2
hit points: 189
speed rating: 100
shield height: 66
shield width: 23
Price is another thing to consider though, and shields get more expensive fast.