not for nothing but... a Vulkoras kills planets faster than a Marza. it has 2 upgrades that enhance sieging. or if you wanted to go the other way with it Phase Missile Swarm is a better direct damage ability than Radiation Bomb. i'd say the Vulk was a much better ship in every way except for Missile Barrage, which as we know, is quite ridiculous.
See, the problem is that Vulk's dps is low compared to Mazda.
Frontal dps of Mazda is 41.5.
Frontal dps of Vulk is 34.
ALL dps of Mazda is 54.5.
ALL dps of Vulk is 41.
Do you see massive difference? And you just can't rely on abilities for damage because you will be out of AM pretty soon.
Not to mention MS of Vulk is not that great.
And no, killing units are more important than bombing planets. Because you can't bomb planets when enemy units are around! (well, unless you want to play as 'pirate')