Plus different accelerations, some have autoslides, armor and sheild ratings, even recharge rates. Not many people seem to bring it up, but gun position is critical to high percentage shots. I rarely miss with the Hellcat V and Arrow compared to the Excalibur which has it's guns further apart, even with autotrack, you still miss smaller ships serveral times on the average melee. In WC4, the Bearcat is the worst, although I don't really care for the Hellcat's new gun positioning.
Earthworm, I gunned down a couple ships with a turret, several corvettes, and a deystroyer that I recall, not to mention fighters. I used the Longow's turret to kill at least one Arrow in WC4, those frigates are easy pickings on strafing runs.
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Don't look conspicuous-it draws fire.