system
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human
[Star Wars] Just what makes a 1.0 class hyperdrive faster than a 2.0 class hyperdrive? Are there trade-offs to having a faster hyperdrive?

I've noticed that the hyperdrive class rating system is kind of all over the place, the Imperial 1 Class Star Destroyer has a class of 2.0 but the Mon Calamari MC 90 has a class 1.0. Why? 
Can smaller vessels be faster? The Nebulon-B, smaller than an MC 90, has a class of 2.0. 

Does having a lower hyperdrive class have any cons when it comes to ship design?
gpt
At least in Legends, military ships generally had the fastest Hyperdrives, followed by industrial freighters and transports, and then civilian ships typically had the slowest classes of hyperdrives.

So at the very least, that seems to indicate that cost is the main drawback of fast hyperdrives. Military powers fork out for it, because being able to rapidly redeploy your capital ships is essential for maintaining control over the galaxy. Industrial and commercial ships generate the profit to make it worthwhile to have a fast hyperdrive. Civilians have to be extremely wealthy or have a great need for speed (for example, a smuggler) to have a high-end hyperdrive - a good civilian hyperdrive may be worth as much as the entire rest of the ship.

Between the Imperial-I and MC90 - the MC90 is a newer design, and effectively took over the role of the Star Destroyer for the New Republic. Since the Imperial-II was also equipped with Class 1.0 hyperdrives (at least in some cases), it's likely that newer military-grade hyperdrives were becoming available around the time of the Galactic Civil War that newer ships were built around, which simply weren't available previously (at least at a reasonable price for outfitting a fleet).