Well, this is the point i was making all along, and why a cobra is much better than a viper. It actually has a decent cargo hold for its size (32 tons in one slot) while still having room for equipment in other slots. A viper has little to no cargo hold unless you strip all the internals for cargo space.
However when i was running a viper i still had 8 tons of cargo, which i saved for when i found expensive drifting so i could sell it, or when i wanted to do some delivery missions as well as combat.
The Cobra has a cargocapacity of 16 tons per internal slot, so you have to sacrifice two internals for 32 ton cargo cap.
And now tell me they are the same size:
You can clearly see that the cobra is a way bigger target.
It is true that the hardpoint layout is personal preference
and the cobra has more internal slots and a stronger hull,
but what is hull?
As soon as your shields are offline your subsystems can take damage.
Byebye cobra generator or engines, while the viper has the stronger shield
and thus can longer withstand suffering critical subsystem damage.
The thing with the viper-shield however is the slow recharge rate,
compared to a cobra.
On the speed i do totally agree, but that is because the cobra has class 4 engines and is easily
below the nominal tonnage of these engines, where the viper has to sacrifice tonnage.