For a beginner player, I STRONGLY recommend Hammerhead over Sunder. The Sunder is a "glass cannon", if you know what that means: it can provide monstrous firepower, but it is much more situational and tricky to play well, with more danger if you mess up and not a lot of ways to get out of a sticky situation.
The Hammerhead, by comparison, is IMHO the best ship for a pilot-in-training to learn in. Not only is it the ship you're taught to fly in the main menu tutorials, it has a balanced mix of armour and shielding, speed and guns, with good loadout flexibility and a foolproof "press F to profit" ship system. It's such a ship that is nearly impossible to build wrong - almost anything works on it to some extent, and it forgives mistakes.
Even if we're not talking a piloted ship but just an AI fleet member, the Sunder requires more careful loadout design and in-combat management than the Hammerhead. Sunders rely on their shields, but that same flux pool is what drives their weapons to insane levels, and as such a Sunder requires a careful balance between fighting and staying back, which (for the AI) generally demands a well thought-out loadout.
As an experienced player, I enjoy both the Hammerhead and Sunder, and in both of them I see flaws and benefits, and places where they work well and not so well. In fact the "Hammerhead/Sunder rivalry" is quite interesting to me. Regardless, for this situation where you're still learning, I suggest the Hammerhead hands-down as something that's really hard to go wrong with.