I find that the entire ship type is completely personal choice. Some go the game solo, while other prefer to only play with friends.. It just completely changes with every person.
I find myself as being a solo person, while at the same time wanting to help people as much as possible.. So my take would be that in every system to start with a storm. If necessary, I will purchase an engineer to help out my buddies.
So I would actually have these ship descriptions..
Storm: Most powerful ship in the game, Best used for grinding and killing mantis; It is fast, deadly, and its item cool-downs are fast enough to keep you swinging like rocky in any fight.
Tank: Most armored ship in the game, best used as target practice for the puny mantis; This ship is very slow, Its cool-downs are slow leaving it unable to destroy the mantis in a quick manner. With shield and aim-scrambler capabilities, it is well worth the purchase. It is easily able to withstand a 5-1 battle against the mantis and has unmatched obesity.
Stun: The most slippery ship, best used to flee or to prevent a fleeing foe; The aggro beacon will draw the mantis in while you make your escape, while the stuns make it very difficult to escape. It's speed capabilities are unmatched as it is equipped with a speed actuator to speed up the cool-down process allowing it to not only shoot faster, but to also use its afterburner more often.
Engineer: The most friendly ship, Best used as a support ship and not as a main attack ship; The engineer has little power to be desired, but makes up for its lack of power with its lack of protective abilities. Not only does it have a repair target, it also has a repair field to repair any and all ally, clan member, squad mate, and/or buddy in the vicinity! It also has its own shield called the protect, this is a special shield as it protects the shielded from stuns! It also may be used on friends as well as yourself! This ship will not last long though, It is best to keep it in the back of the battle lines while healing the wounded on the front lines!
That's about the best I could sum it up for you. Hope you enjoyed! ^^