The Siegestone tower also fires out a large area-of-effect attack. The damage on it is considerable, but the rate of fire is very low. This makes it very good at clearly out enemy Soldier waves, who tend to cluster and will not evade the Area of Effect (AOE). It is also an excellent deterrent for enemy Guardians, because of the severity of damage. However, because the rate of fire is fairly low, and that the AOE is telegraphed, it can make it easy for enemy Guardians to evade the attack.
Instead, the Siegestone tower is best to destroying enemy Soldier waves, especially if you find yourself being pushed. If you find that lane parity is relatively even, the Quickfire and Splitshot towers are superior options to quickly killing assaulting enemy Guardians.