system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How much different is an unmodified YT-1300 from something such as the Millenium Falcon?

The Falcon being a YT-1300 with a vast array of modifications made to it over the years.  How extremely have these additions changed it from its default appearance and functionality?
gpt
More or less every technical aspect of the Falcon has been enhanced.  It's guns, armor and shielding are equivalent to that of a military vessel.  It has improved computers.  And specialized compartments that can hide contraband from detection.  But, the most impressive improvement is the hyperdrive; which is essentially the best hyperdrive that you could fit on a ship of that size.  It isn't far from the truth when Han says the Falcon is the fastest ship in the galaxy.  

As for appearance it doesn't standout much.  It looks like a junky YT-1300 that has been jury rigged to function.  As an analogy it would look like a pickup truck with different colored doors and hood and a bungie cord holding the tailgate on.  You wouldn't suspect that under the hood was an 1800 hp engine.  The Millennium Falcon has been modified to peak performance, but wouldn't cause a customs official to give it a second look.